Chicago, October 19 - 22, 2010
Paul King
@paulk_asert
Groovy Committer
ASERT, Australia
Groovy.DSLs(from: beginner,
to: ex...
Topics
Introduction
• Groovy DSL Features
• A Week In The Life Of DSL INC
• Summary
• More Info
DSLs 2010 - 2
©ASERT2006-...
What is a DSL?
• A domain-specific language is a
programming language or executable
specification language that offers, th...
1. e4 e5
2. Nf3 Nc6
3. Bb5 a6
L2 U F-1 B L2 F B -1 U L2
Visual!
Technical Examples
Source: Applying minilanguages: http://www.faqs.org/docs/artu/ch08s02.html
<?xml version="1.0"?>
<xsl:s...
Origins
• It has always been a
holy grail of computer
users to be able to
speak directly to our
computers
• Different lang...
Origins
• It has always been a
holy grail of computer
users to be able to
speak directly to our
computers
DSLs 2010 - 9
ht...
Origins: LISP & Smalltalk
“In Lisp, you don’t just write your
program down toward the language,
you also build the languag...
Origins: Minilanguages...
Source: The Art of Unix Programming:Taxonomy of languages: http://www.faqs.org/docs/artu/ch08s01...
...Origins: Minilanguages
PowerPoint DSL for previous slide
import builder.PowerPointBuilder
def name = 'minilanguages'
as...
Subject Matter Experts,
Business Analysts...
HAI CAN HAS STDIO?
I HAS A VAR
IM IN YR LOOP
UP VAR!!1
VISIBLE VAR
IZ VAR BIGGER THAN 10?
KTHXBYE
IM OUTTA YR LOOP
KTHXBYE...
And in the end...
nobody understands
each other
DSL: a potential solution?
1616
• Use a more expressive language than a
general purpose one
• Share a common metaphor of
u...
17
Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited.
Towa...
18
Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited.
Towa...
Why a DSL?
• Advantages:
– Domain experts can
understand, validate, modify,
and often even develop DSL
programs
– Somewhat...
DSL usage patterns...
• Internal (uses a general purpose language)
– AKA embedded
– Can be a subset or superset
– Can be g...
...DSL usage patterns...
Source: DSLs in Action, Debasish Ghosh, Manning now in MEAP DSLs 2010 - 21
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...DSL usage patterns
Source: DSLs in Action, Debasish Ghosh, Manning now in MEAP DSLs 2010 - 22
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DSL usage patterns (Advanced)
Source: http://www.spinellis.gr/pubs/jrnl/2000-JSS-DSLPatterns/html/dslpat.html
See: Diomidi...
DSLs 2010 - 24
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What is Groovy?
• “Groovy is like a super version
of Java. It can leverage Java's
enterpris...
DSLs 2010 - 25
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Groovy Goodies Overview
• Fully object oriented
• Closures: reusable
and assignable
pieces ...
Growing Acceptance …
A slow and steady start but now gaining in
momentum, maturity and mindshare
Now free
DSLs 2010 - 27
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The Landscape of JVM Languages
Java bytecode calls
for static types
Dynamic features call
f...
DSLs 2010 - 28
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Groovy Starter
System.out.println("Hello, World!"); // supports Java syntax
println 'Hello,...
A Better Java...
DSLs 2010 - 29
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import java.util.List;
import java.util.ArrayList;
class Erase {
private L...
...A Better Java...
DSLs 2010 - 30
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import java.util.List;
import java.util.ArrayList;
class Erase {
privat...
...A Better Java...
DSLs 2010 - 31
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class Erase {
private List removeLongerThan(List strings, int length) {...
...A Better Java...
DSLs 2010 - 32
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class Erase {
private List removeLongerThan(List strings, int length) {...
...A Better Java...
DSLs 2010 - 33
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def removeLongerThan(strings, length) {
def result = new ArrayList()
fo...
...A Better Java...
DSLs 2010 - 34
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def removeLongerThan(strings, length) {
def result = new ArrayList()
fo...
...A Better Java...
DSLs 2010 - 35
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def removeLongerThan(strings, length) {
strings.findAll{ it.size() <= l...
...A Better Java...
DSLs 2010 - 36
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def removeLongerThan(strings, length) {
strings.findAll{ it.size() <= l...
...A Better Java...
DSLs 2010 - 37
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names = ["Ted", "Fred", "Jed", "Ned"]
println names
shortNames = names....
...A Better Java
DSLs 2010 - 38
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names = ["Ted", "Fred", "Jed", "Ned"]
println names
shortNames = names.fin...
Grapes / Grab
DSLs 2010 - 39
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// Google Collections example
@Grab('com.google.collections:google-collection...
Malleable Syntax
DSLs 2010 - 40
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order to buy 200.shares of GOOG {
limitPrice 500
allOrNone false
at the va...
41
Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited.
Real...
42
Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited.
DSLs...
Testing DSLs: Spock...
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DSLs 2010 - 43
...Testing DSLs: Spock...
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• Testing framework for Java and Groovy
• Highly expressive specification langua...
...Testing DSLs: Spock...
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import com.gargoylesoftware.htmlunit.WebClient
import spock.lang.*
import org.ju...
... Testing DSLs: Spock
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...
then:
page.titleText == 'Welcome to SimpBlog'
result.getElementsByTagName('h1'...
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Testing DSLs: EasyB…
• Description: BDD, Rspec-like testing library
narrative 'segment flown', {
as_a 'fre...
…Testing DSLs: EasyB
• When run will be marked as pending
– perfect for ATDD
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scenario "Bart posts a new bl...
Testing DSLS: Cucumber...
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# language: en
@newpost
Feature: New Blog Post
In order to create a new blog ent...
... Testing DSLS: Cucumber...
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DSLs 2010 - 50
...Testing DSLS: Cucumber
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import com.gargoylesoftware.htmlunit.WebClient
this.metaClass.mixin(cuke4duke.Gr...
Grails Criteria
DSLs 2010 - 52
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// Account is a POJO in our domain/model
def c = Account.createCriteria()
d...
Grails Criteria Example
DSLs 2010 - 53
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// Book is a POJO in our domain/model
def book = Book.findByTitle("...
Grails Bean Builder Example
DSLs 2010 - 54
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bb.beans {
marge(Person) {
name = "marge"
husband = { Person p ...
GPars...
import static org.gparallelizer.actors.pooledActors.PooledActors.*
// create a new actor that prints out received...
...GPars
import static org.gparallelizer.dataflow.DataFlow.thread
final def x = new DataFlowVariable()
final def y = new D...
Topics
• Introduction
Groovy DSL Features
• A Week In The Life Of DSL INC
• Summary
• More Info
DSLs 2010 - 57
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Groovy DSL Features
DSLs 2010 - 58
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Import / Import Static
• Imports
• Static Imports
DSLs 2010 - 59
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@Grab('com.google.collections:google-coll...
Static Imports...
DSLs 2010 - 60
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import groovy.swing.SwingXBuilder
import static java.awt.Color.*
import s...
...Static Imports...
DSLs 2010 - 61
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import groovy.swing.SwingXBuilder
import static java.awt.Color.*
impor...
...Static Imports...
DSLs 2010 - 62
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import groovy.swing.SwingXBuilder
import static java.awt.Color.*
impor...
...Static Imports...
DSLs 2010 - 63
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Source: http://www.thedoghousediaries.com/?p=1406
...Static Imports
DSLs 2010 - 64
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import groovy.swing.SwingXBuilder
import static java.lang.Math.*
import s...
Literal Syntax Conventions
• Lists
– Special syntax for list literals
– Additional common methods (operator overloading)
•...
Literal Syntax Conventions in DSLs
DSLs 2010 - 66
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import static java.util.Calendar.getInstance as getNow
i...
Compact Syntax...
• Java
• Groovy
DSLs 2010 - 67
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public class BuySharesJava {
public static void buyShares...
...Compact Syntax...
• Java
• Groovy
DSLs 2010 - 68
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import java.util.Date;
import java.util.HashMap;
impor...
...Compact Syntax
• Java
• Groovy
DSLs 2010 - 69
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import java.util.Date;
public class ProcessStrongCustomer...
Using With Example
DSLs 2010 - 70
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letters = ['a', 'b', 'c']
range = 'b'..'d'
letters.with {
add 'd'
remove...
Closures...
• Traditional mainstream languages
– Data can be stored in variables, passed around,
combined in structured wa...
...Closures...
DSLs 2010 - 72
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int myConst = 4
def multiplier = { number -> number * myConst }
assert multi...
...Closures...
DSLs 2010 - 73
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int myConst = 4
def multiplier = { number -> number * myConst }
assert multi...
...Closures...
DSLs 2010 - 74
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int myConst = 4
def multiplier = { number -> number * myConst }
assert multi...
...Closures...
DSLs 2010 - 75
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int myConst = 4
def multiplier = { number -> number * myConst }
assert multi...
...Closures...
DSLs 2010 - 76
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int myConst = 4
def multiplier = { number -> number * myConst }
assert multi...
...Closures...
DSLs 2010 - 77
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int myConst = 4
def multiplier = { number -> number * myConst }
assert multi...
Closures in DSLs...
DSLs 2010 - 78
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import static java.util.Calendar.*
def cart1 = [
[qty: 3, unitPrice: 50...
... Closures in DSLs...
DSLs 2010 - 79
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// ...
def noDiscount = { it.unitPrice * it.qty }
def tenPercentOff...
... Closures in DSLs...
DSLs 2010 - 80
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// ...
def noDiscount = { it.unitPrice * it.qty }
def tenPercentOff...
... Closures in DSLs
DSLs 2010 - 81
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// ...
def specials = [noDiscount, tenPercentOffAll,
tenPercentOffGift...
Operator Overloading Example
DSLs 2010 - 82
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BigDecimal a = new BigDecimal(3.5d);
BigDecimal b = new BigDec...
Groovy Lab Example
DSLs 2010 - 83
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// require GroovyLab
import static org.math.array.Matrix.*
import static...
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Better Control Structures: Switch Poker…
suits = 'SHDC'
ranks = '23456789TJQKA'
suit = { String card -> su...
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…Better Control Structures: Switch Poker…
// ...
flush = { List cards -> cards.groupBy(suit).size() == 1 }...
©ASERT2006-2010
… Better Control Structures: Switch Poker
// ...
def rankHand(List cards) {
switch (cards) {
case straight...
Type Transformation Example
DSLs 2010 - 87
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class InventoryItem {
def weight, name
InventoryItem(Map m) {
t...
DSLs 2010 - 88
Groovy DSL Features
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Metaprogramming
• Runtime Metaprogramming
– Categories including DGM
– invokeMethod, methodMissing, getProperty
– GroovyIn...
DSLs 2010 - 90
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Builders…
<html>
<head>
<title>Hello</title>
</head>
<body>
<ul>
<li>world 1</li>
<li>world...
...Builders…
DSLs 2010 - 91
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def colors = ['red','darkOrange','blue','darkGreen']
(0..3).each { index ->
st...
…Builders
new AntBuilder().with {
echo(file:'Temp.java', '''
class Temp {
public static void main(String[] args) {
System....
93
Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited.
A bu...
DSLs 2010 - 94
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ExpandoMetaClass…
import static java.lang.Character.isUpperCase
String.metaClass.swapCase =...
DSLs 2010 - 95
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…ExpandoMetaClass
class Person {
String name
}
class MortgageLender {
def borrowMoney() {
"...
Adding your own control structures
• Thread enhancement
DSLs 2010 - 96
ROCK!
. 25
. 33
. 34
. 35
. 36
.. 131
.. 134
.. 137...
EMC DSL…
DSLs 2010 - 97
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...EMC Neo4j DSL…
DSLs 2010 - 98
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@GrabResolver(name= 'neo4j-public-repo', root= 'http://m2.neo4j.org')
@Gr...
…EMC Neo4j DSL
DSLs 2010 - 99
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// ...
def graphDb = new EmbeddedGraphDatabase("graphdb")
def tx = graphDb.b...
Game example...
DSLs 2010 - 100
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// Trying out the game DSL idea by Sten Anderson from:
// http://blogs.cit...
...Game example...
DSLs 2010 - 101
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...
class Room {
def description
def contents = []
}
...
...Game example...
DSLs 2010 - 102
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...
class Player {
def currentRoom
def inventory = []
void look() {
pri...
...Game example...
DSLs 2010 - 103
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...
void drop(item) {
if (inventory?.remove(item)) {
currentRoom?.conte...
...Game example...
DSLs 2010 - 104
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...
Room plainRoom = new Room(description:'a plain white room',
content...
...Game example
DSLs 2010 - 105
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...
// now try some error conditions
plainRoom.description = null
player.w...
GEP3 example...
DSLs 2010 - 106
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Object.metaClass.please =
{ clos -> clos(delegate) }
Object.metaClass.the ...
...GEP3 example...
DSLs 2010 - 107
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Object.metaClass.of =
{ delegate[0](delegate[1](it)) }
Object.metaClass...
...GEP3 example...
DSLs 2010 - 108
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show = { println it }
square_root = { Math.sqrt(it) }
def please(action...
...GEP3 example...
DSLs 2010 - 109
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// Japanese DSL using GEP3 rules
Object.metaClass.を =
Object.metaClass....
...GEP3 example
DSLs 2010 - 110
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// source: http://d.hatena.ne.jp/uehaj/20100919/1284906117
// http://groov...
Medical Prescription DSL…
DSLs 2010 - 111
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class Drug {
String name
String toString() { name }
}
class Meas...
…Medical Prescription DSL…
DSLs 2010 - 112
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// ...
// ---- DSL implementation -----------------------------...
…Medical Prescription DSL
DSLs 2010 - 113
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// ...
// ---- DSL -------------------------------
take 2.pills ...
Groovy DSL Features
DSLs 2010 - 114
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Transformation
AST Transformations
• With metaprogramming, Groovy‟s able to
modify the behaviour of programs... at
runtime
• AST Transfor...
Better Design Patterns: Immutable...
• Java Immutable Class
– As per Joshua Bloch
Effective Java
DSLs 2010 - 116
©ASERT200...
...Better Design Patterns: Immutable...
• Java Immutable Class
– As per Joshua Bloch
Effective Java
DSLs 2010 - 117
©ASERT...
...Better Design Patterns: Immutable
DSLs 2010 - 118
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@Immutable class Punter {
String first, last
}
Spock
DSLs 2010 - 119
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def "length of Spock's & his friends' names"() {
expect:
name.size() == length
where...
AST Builder
• Numerous approaches, still evolving.
“From code” approach:
• Produces:
def result = new AstBuilder().buildFr...
©ASERT2006-2010
EasyB…
• Description: BDD, Rspec-like testing library
narrative 'segment flown', {
as_a 'frequent flyer'
i...
©ASERT2006-2010
…EasyB
• Description: BDD, Rspec-like testing library
examples "The number #{number}' should be converted ...
EasyB Preprocessing...
• EasyB supports either of these:
• But we would like this:
given ("some data") {
println '... sett...
...EasyB Preprocessing...
String addCommas(text) {
def pattern =
~/(.*)(given|when|then) "([^"]*(.[^"]*)*)" {(.*)/
def rep...
...EasyB Preprocessing
class SourceModifierParserPlugin extends AntlrParserPlugin {
Reduction parseCST(SourceUnit sourceUn...
GParsec...
• Miniature parsers
• Parser Combinators
def isLetter = { ch -> return Character.isLetter(ch) }
def isDigit = {...
...GParsec...
• BNF
• Groovy definitions
variableDeclarator :
identifier ( '=' expression )?
variableDefinitions :
variabl...
...GParsec
• satisfyC: combinator consumes a single input when its
predicate succeeds
• altC (alt3C, altCs): is the choice...
Using External Parsers
DSLs 2010 - 129
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import static com.mdimension.jchronic.Chronic.parse
def span = pars...
Topics
• Introduction
• Groovy DSL Features
A Week In The Life Of DSL INC
• Summary
• More Info
DSLs 2010 - 130
©ASERT200...
MONDAY
DSLs 2010 - 131
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Currency DSL…
DSLs 2010 - 132
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From: customer@acme.org
To: Guillaume
Subject: Project Request
Dear Guillaum...
…Currency DSL...
DSLs 2010 - 133
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enum Coin {
penny(1), nickel(5), dime(10), quarter(25)
Coin(int value) { ...
…Currency DSL…
DSLs 2010 - 134
©ASERT2006-2010
From: customer@acme.org
To: Guillaume
Subject: Project Request
Dear Guillau...
...Currency DSL...
DSLs 2010 - 135
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class CoinMath {
static multiply(Integer self, Coin c) {
self * c.value...
…Currency DSL…
DSLs 2010 - 136
©ASERT2006-2010
From: customer@acme.org
To: Guillaume
Subject: Project Request
Dear Guillau...
... Currency DSL
DSLs 2010 - 137
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class CoinValues {
static get(Integer self, String name) {
self * Coin."$...
TUESDAY
DSLs 2010 - 138
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http://www.google.com/imgres?imgurl=http://i733.photobucket.com/albums/ww336/snake...
Business logic DSL…
DSLs 2010 - 139
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From: customer@acme.org
To: Paul King
Subject: Project Request
Dear Pa...
…Business logic DSL…
• Options
– Embedded Groovy
– Regex parser
– Antlr parser
– Split / StringTokenizer
– Parser combinat...
… Business logic DSL …
DSLs 2010 - 141
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From: customer@acme.org
To: Paul King
Subject: Project Request
Date...
… Business logic DSL …
DSLs 2010 - 142
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def shell = new GroovyShell()
shell.evaluate('''
price = 3
quantity...
… Business logic DSL …
DSLs 2010 - 143
©ASERT2006-2010
From: customer@acme.org
To: Paul King
Subject: Project Request
Date...
… Business logic DSL …
DSLs 2010 - 144
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class CustomerShell {
Object evaluate(String text) {
try {
def load...
… Business logic DSL
DSLs 2010 - 145
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def shell = new CustomerShell()
shell.evaluate('''
price = 3
quantity...
WEDNESDAY
DSLs 2010 - 146
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http://www.crystalscomments.com/1/days/wednesday/animals/006.jpg
Stock Exchange Order DSL…
DSLs 2010 - 147
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Example inspired from DSLs in Action: http://www.manning.com/gho...
… Stock Exchange Order DSL…
DSLs 2010 - 148
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// ----- Implementation of the Fluent API -----
enum Action { ...
…Stock Exchange Order DSL…
DSLs 2010 - 149
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From: customer@finance-broker.org
To: Guillaume
Subject: Projec...
…Stock Exchange Order DSL…
DSLs 2010 - 150
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class Order {
def security
def quantity
def limitPrice
def allO...
…Stock Exchange Order DSL…
DSLs 2010 - 151
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...
def getTo() { this }
def valueAs(closure) {
value = closure...
…Stock Exchange Order DSL…
DSLs 2010 - 152
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From: customer@finance-broker.org
To: Guillaume
Subject: Projec...
…Stock Exchange Order DSL…
DSLs 2010 - 153
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class Order {
...
def allOrNone
def valueCalculation
def bs
......
…Stock Exchange Order DSL…
DSLs 2010 - 154
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From: customer@finance-broker.org
To: Guillaume
Subject: Projec...
…Stock Exchange Order DSL…
DSLs 2010 - 155
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// Characteristics of the order: "of GOOG {...}"
def of(Securit...
…Stock Exchange Order DSL…
DSLs 2010 - 156
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// ...
class Security {
String name
}
class SecurityAndCharacte...
…Stock Exchange Order DSL…
DSLs 2010 - 157
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// ---- Stock exchange orders DSL ----
order to buy 200.shares ...
…Stock Exchange Order DSL
DSLs 2010 - 158
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From: customer@finance-broker.org
To: Guillaume
Subject: Project...
THURSDAY
DSLs 2010 - 159
©ASERT2006-2010
http://t1.gstatic.com/images?q=tbn:_VBloEP8YC-6IM:http://msp248.photobucket.com/a...
Einstein‟s Riddle DSL …
DSLs 2010 - 160
©ASERT2006-2010
From: customer@acme.org
To: Paul King
Subject: Project Request
Dat...
Einstein‟s Riddle…
• Wikipedia: The zebra puzzle is a well-
known logic puzzle
– It is often called Einstein's Puzzle or E...
…Einstein‟s Riddle
DSLs 2010 - 162
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• Some premises:
– The British person lives in the red house
– The Swed...
Einstein‟s Riddle : Prolog
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% from http://www.baptiste-wicht.com/2010/09/solve-einsteins-riddle-using-prolo...
Einstein‟s Riddle DSL …
DSLs 2010 - 164
©ASERT2006-2010
From: customer@acme.org
To: Paul King
Subject: Project Request
Dat...
Einstein‟s Riddle : Polyglot
©ASERT2006-2010
@GrabResolver('http://dev.inf.unideb.hu:8090/archiva/repository/internal')
//...
Einstein‟s Riddle DSL …
DSLs 2010 - 166
©ASERT2006-2010
From: customer@acme.org
To: Paul King
Subject: Project Request
Dat...
Einstein‟s Riddle : Polyglot w/ DSL…
©ASERT2006-2010
// define some domain classes and objects
enum Pet { dog, cat, bird, ...
…Einstein‟s Riddle : Polyglot w/ DSL…
©ASERT2006-2010
DSLs 2010 - 168
// define some helper methods (our interface to prol...
…Einstein‟s Riddle : Polyglot w/ DSL…
©ASERT2006-2010
DSLs 2010 - 169
// now implement DSL in terms of helper methods
def ...
…Einstein‟s Riddle : Polyglot w/ DSL…
©ASERT2006-2010
DSLs 2010 - 170
// now define the DSL
the man from the centre house ...
Einstein‟s Riddle DSL …
DSLs 2010 - 171
©ASERT2006-2010
From: customer@acme.org
To: Paul King
Subject: Project Request
Dat...
…Einstein‟s Riddle : Polyglot w/ DSL…
©ASERT2006-2010
DSLs 2010 - 172
// now implement DSL in terms of helper methods
def ...
…Einstein‟s Riddle : Polyglot w/ DSL…
• Some parts of our DSL are automatically
statically inferred, e.g. typing „bl‟ and ...
…Einstein‟s Riddle : Polyglot w/ DSL
©ASERT2006-2010
DSLs 2010 - 174
class HousePlaceHolder {
def c1, script
def house(_is...
Einstein‟s Riddle DSL …
DSLs 2010 - 175
©ASERT2006-2010
From: customer@acme.org
To: Paul King
Subject: Project Request
Dat...
Einstein‟s Riddle : Choco w/ DSL…
©ASERT2006-2010
DSLs 2010 - 176
@GrabResolver('http://www.emn.fr/z-info/choco-solver/mvn...
…Einstein‟s Riddle : Choco w/ DSL…
©ASERT2006-2010
DSLs 2010 - 177
// define DSL (simplistic non-refactored version)
def n...
…Einstein‟s Riddle : Choco w/ DSL…
©ASERT2006-2010
DSLs 2010 - 178
// define rules
m += all pets are different
m += all co...
…Einstein‟s Riddle : Choco w/ DSL
• Output:
DSLs 2010 - 179
©ASERT2006-2010
def pretty(s, c, arr, i) { c.values().find{
it...
FRIDAY
DSLs 2010 - 180
©ASERT2006-2010
http://t3.gstatic.com/images?q=tbn:mgkj1lXpQ2-uWM:http://i298.photobucket.com/album...
Important business meetings all afternoon!
DSLs 2010 - 181
©ASERT2006-2010
http://www.flickr.com/photos/bobswanson/5093775...
Topics
• Introduction
• Groovy DSL Features
• A Week In The Life Of DSL INC
Summary
• More Info
DSLs 2010 - 182
©ASERT200...
Some Finishing Guidelines
• Language and program evolve together …
In the end your program will look as if the
language ha...
Start small, with key concepts
Beware over-engineering!
Grow your language
progressively
Get your hands dirty
Play with the end-users
Let your DSL fly,
it‟s not yours, it‟s theirs!
Tight feedback loop
Iterative process
Stay humble,
You can‟t get it right the 1st time.
Don‟t design alone at your desk
Involve the end users from the start
Playing it safe in a sandbox
Topics
• Introduction
• Groovy DSL Features
• A Week In The Life Of DSL INC
• Summary
More Info
DSLs 2010 - 191
©ASERT200...
Further Info…
DSLs 2010 - 192
©ASERT2006-2010
• Compilers : Principles, Techniques,
and Tools/ Edition 2, Alfred Aho, Ravi...
…Further Info
DSLs 2010 - 193
©ASERT2006-2010
• A model-driven framework for domain
specific languages, Martin Karlsch
• D...
GinA 2ed “ReGinA” is coming!
DSLs 2010 - 194
Contains a
chapter on
DSLs!
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groovy DSLs from beginner to expert

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Paul King and Guillaume Laforge present Groovy.DSLs(from:beginner, to:expert) at SpringOne2GX in Chicago in October 2010

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groovy DSLs from beginner to expert

  1. 1. Chicago, October 19 - 22, 2010 Paul King @paulk_asert Groovy Committer ASERT, Australia Groovy.DSLs(from: beginner, to: expert) Guillaume Laforge @glaforge Groovy Project Manager SpringSource / VMWare
  2. 2. Topics Introduction • Groovy DSL Features • A Week In The Life Of DSL INC • Summary • More Info DSLs 2010 - 2 ©ASERT2006-2010
  3. 3. What is a DSL? • A domain-specific language is a programming language or executable specification language that offers, through appropriate notations and abstractions, expressive power focused on, and usually restricted to, a particular problem domain – In contrast, general-purpose languages are created to solve problems in many domains – Somewhere between declarative data and a full blown general- purpose programming language (GPL) – AKA: fluent / human interfaces, language oriented programming, problem-oriented languages, little / mini languages, macros, business natural languages Sources: http://en.wikipedia.org/wiki/Domain-specific_language van Deursen, A., Klint, P., Visser, J.: Domain-specific languages: an annotated bibliography. ACM SIGPLAN Notices 35 (2000) 26–36 ©ASERT2006-2010
  4. 4. 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6
  5. 5. L2 U F-1 B L2 F B -1 U L2
  6. 6. Visual!
  7. 7. Technical Examples Source: Applying minilanguages: http://www.faqs.org/docs/artu/ch08s02.html <?xml version="1.0"?> <xsl:stylesheetversion="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:output method="xml"/> <xsl:template match="*"> <xsl:element name="{name()}"> <xsl:for-each select="@*"> <xsl:element name="{name()}"> <xsl:value-of select="."/> </xsl:element> </xsl:for-each> <xsl:apply-templates select="*|text()"/> </xsl:element> </xsl:template> </xsl:stylesheet> cat thesis.ms | chem | tbl | refer | grap | pic | eqn | groff -Tps > thesis.ps <?xml version="1.0"?> <GTK-Interface> <widget> <class>GtkWindow</class> <name>HelloWindow</name> <border_width>5</border_width> <Signal> <name>destroy</name> <handler>gtk_main_quit</handler> </Signal> <title>Hello</title> <type>GTK_WINDOW_TOPLEVEL</type> <position>GTK_WIN_POS_NONE</position> <allow_shrink>True</allow_shrink> <allow_grow>True</allow_grow> <auto_shrink>False</auto_shrink> <widget> <class>GtkButton</class> <name>Hello World</name> <can_focus>True</can_focus> <label>Hello World</label> </widget> </widget> </GTK-Interface> # Poll this site first each cycle. poll pop.provider.net proto pop3 user "jsmith" with pass "secret1" is "smith" here user jones with pass "secret2" is "jjones" here with options keep # Poll this site second, unless Lord Voldemort zaps us first. poll billywig.hogwarts.com with proto imap: user harry_potter with pass "floo" is harry_potter here # Poll this site third in the cycle. # Password will be fetched from ~/.netrc poll mailhost.net with proto imap: user esr is esr here Glade Troff XSLT fetchmail Regex "x.z?z{1,3}y" SQL SELECT * FROM TABLE WHERE NAME LIKE '%SMI' ORDER BY NAME DSLs 2010 - 7
  8. 8. Origins • It has always been a holy grail of computer users to be able to speak directly to our computers • Different languages have pushed the boundaries further than others – APT for numerically controlled machine tools (1957) – BNF (1959), COBOL, 4GLs – LISP & Smalltalk – Unix "little languages" DSLs 2010 - 8 ©ASERT2006-2010
  9. 9. Origins • It has always been a holy grail of computer users to be able to speak directly to our computers DSLs 2010 - 9 http://dsal.uchicago.edu/reference/gazetteer/pager.html?objectid=DS405.1.I34_V02_298.gif ©ASERT2006-2010
  10. 10. Origins: LISP & Smalltalk “In Lisp, you don’t just write your program down toward the language, you also build the language up toward your program” - Paul Graham “When [Smalltalk] is used to describe an application system, the developer extends Smalltalk, creating a domain-specific language by adding a new vocabulary of language elements ...” - Adele Goldberg DSLs 2010 - 10 ©ASERT2006-2010
  11. 11. Origins: Minilanguages... Source: The Art of Unix Programming:Taxonomy of languages: http://www.faqs.org/docs/artu/ch08s01.html %!PS-Adobe-3.0 %%Creator: groff version 1.20.1 ... 597.6 12 72 12 DL(increasing loopiness)297.71 8.2 Q(/etc/passwd)102.67 94.6 Q(.ne)110.715 106.6 Q(wsrc)-.25 E(SNG)195.2 100.6 Q(re)243.8 94.6 Q (ge)-.15 E(xps)-.15 E(Glade)247.26 106.6 Q(m4)306.81 58.6 Q -1(Ya)303.43 70.6 S(cc)1 E(Le)305.5 82.6 Q(x)-.15 E(mak)302.42 94.6 Q(e)-.1 E(XSL) 301.16 106.6 Q(T)-.92 E(pic)307.09 118.6 Q(tbl)307.92 130.6 Q(eqn)305.98 142.6 Q(fetchmail)344.715 82.6 Q -.15(aw)355.345 94.6 S(k).15 E(trof) 354.84 106.6 Q(f)-.25 E(Postscript)343.875 118.6 Q(dc)412.88 94.6 Q(bc) 412.88 106.6 Q(Emacs Lisp)462.53 94.6 Q(Ja)465.395 106.6 Q -.25(va)-.2 G (Script).25 E(sh)529.075 94.6 Q(tcl)528.52 106.6 Q(Perl)565.065 88.6 Q (Python)558.95 100.6 Q(Ja)564.46 112.6 Q -.25(va)-.2 G 0 Cg EP %%Trailer end %%EOF Input DSL: pic for above picture Output "DSL": Postscript for above picture # Minilanguage taxonomy # Base ellipses define smallellipse {ellipse width 3.0 height 1.5} M: ellipse width 3.0 height 1.8 fill 0.2 line from M.n to M.s dashed D: smallellipse() with .e at M.w + (0.8, 0) line from D.n to D.s dashed I: smallellipse() with .w at M.e - (0.8, 0) # Arrow headings arrow from D.w + (0.4, 0.8) to D.e + (-0.4, 0.8) "flat to structured" "" at last arrow.c ... # Interpreters "Emacs Lisp" "JavaScript" at 0.25 between M.e and I.e "sh" "tcl" at 0.55 between M.e and I.e "Perl" "Python" "Java" at 0.8 between M.e and I.e DSLs 2010 - 11
  12. 12. ...Origins: Minilanguages PowerPoint DSL for previous slide import builder.PowerPointBuilder def name = 'minilanguages' assert new File("${name}.pic').exists() "groff -e -p ${name}.pic > ${name}.ps".execute() "gs -q -sDEVICE='ppmraw' -g2600x3500 -r300x300 -sOutputFile='-' -dBATCH ↵ –dNOPAUSE ${name}.ps | pnmcrop | ppmtogif > ${name}.gif".execute() def builder = new PowerPointBuilder() // Adapted from Erik Pragt builder.slideshow(filename: 'DSLsInGroovy_MiniLanguages.ppt') { slide(title: 'Origins: Minilanguages...') { image( origin: [0, 15], src: "${name}.gif", caption: 'Source: The Art of Unix Programming:Taxonomy...' ) textbox( origin: [5, 100], text: new File("${name}.pic").text, caption: 'Input DSL: pic for above picture' ) textbox( origin: [115, 100], text: new File("${name}.ps").text, caption: 'Output "DSL": Postscript for above picture' ) } } DSLs 2010 - 12
  13. 13. Subject Matter Experts, Business Analysts...
  14. 14. HAI CAN HAS STDIO? I HAS A VAR IM IN YR LOOP UP VAR!!1 VISIBLE VAR IZ VAR BIGGER THAN 10? KTHXBYE IM OUTTA YR LOOP KTHXBYE Developer producing LOLCODE
  15. 15. And in the end... nobody understands each other
  16. 16. DSL: a potential solution? 1616 • Use a more expressive language than a general purpose one • Share a common metaphor of understanding between developers and subject matter experts • Have domain experts help with the design of the business logic of an application • Avoid cluttering business code with too much boilerplate technical code • Cleanly separate business logic from application code • Let business rules have their own lifecycle
  17. 17. 17 Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. Towards more readibility (1) 20% 17
  18. 18. 18 Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. Towards more readibility (2) 80%
  19. 19. Why a DSL? • Advantages: – Domain experts can understand, validate, modify, and often even develop DSL programs – Somewhat self-documenting – Enhance quality, productivity, reliability, maintainability, portability and reusability – Safety; as long as the language constructs are safe any sentence written with them can be considered safe • Disadvantages: – Learning cost vs. limited applicability – Cost of designing, implementing & maintaining DSL as well as the tools/IDEs – Attaining proper scope – Trade-offs between domain- specificity and general- purpose programming language constructs – Efficiency costs – Proliferation of similar non- standard DSLs, i.e. different but similar DSLs used within two insurance companies Source: http://en.wikipedia.org/wiki/Domain-specific_language DSLs 2010 - 19 ©ASERT2006-2010
  20. 20. DSL usage patterns... • Internal (uses a general purpose language) – AKA embedded – Can be a subset or superset – Can be generated/converted from other "language" – Numerous mechanisms to make as close to the domain as possible • External (custom language) – May involve writing your own traditional parser – Using parser combinators – Interpreting – String grepping • Other characteristics – Functional vs OO DSLs 2010 - 20 ©ASERT2006-2010
  21. 21. ...DSL usage patterns... Source: DSLs in Action, Debasish Ghosh, Manning now in MEAP DSLs 2010 - 21 ©ASERT2006-2010
  22. 22. ...DSL usage patterns Source: DSLs in Action, Debasish Ghosh, Manning now in MEAP DSLs 2010 - 22 ©ASERT2006-2010
  23. 23. DSL usage patterns (Advanced) Source: http://www.spinellis.gr/pubs/jrnl/2000-JSS-DSLPatterns/html/dslpat.html See: Diomidis Spinellis. Notable design patterns for domain specific languages. Journal of Systems and Software, 56(1):91–99, February 2001. ©ASERT2006-2010
  24. 24. DSLs 2010 - 24 ©ASERT2006-2010 What is Groovy? • “Groovy is like a super version of Java. It can leverage Java's enterprise capabilities but also has cool productivity features like closures, DSL support, builders and dynamic typing.” Groovy = Java – boiler plate code + optional dynamic typing + closures + domain specific languages + builders + metaprogramming
  25. 25. DSLs 2010 - 25 ©ASERT2006-2010 Groovy Goodies Overview • Fully object oriented • Closures: reusable and assignable pieces of code • Operators can be overloaded • Multimethods • Literal declaration for lists (arrays), maps, ranges and regular expressions • GPath: efficient object navigation • GroovyBeans • grep and switch • Templates, builder, swing, Ant, markup, XML, SQL, XML-RPC, Scriptom, Grails, tests, Mocks
  26. 26. Growing Acceptance … A slow and steady start but now gaining in momentum, maturity and mindshare Now free
  27. 27. DSLs 2010 - 27 ©ASERT2006-2010 The Landscape of JVM Languages Java bytecode calls for static types Dynamic features call for dynamic types optional static types The terms “Java Virtual Machine” and “JVM” mean a Virtual Machine for the Java™ platform.
  28. 28. DSLs 2010 - 28 ©ASERT2006-2010 Groovy Starter System.out.println("Hello, World!"); // supports Java syntax println 'Hello, World!' // but can remove some syntax String name = 'Guillaume' // Explicit typing/awareness println "$name, I'll get the car." // Gstring (interpolation) def longer = """${name}, the car is in the next row.""" // multi-line, implicit type assert 0.5 == 1/2 // BigDecimal equals() assert 0.1 + 0.2 == 0.3 // and arithmetic def printSize(obj) { // implicit/duck typing print obj?.size() // safe dereferencing } def pets = ['ant', 'bee', 'cat'] // native list syntax pets.each { pet -> // closure support assert pet < 'dog' // overloading '<' on String } // or: for (pet in pets)...
  29. 29. A Better Java... DSLs 2010 - 29 ©ASERT2006-2010 import java.util.List; import java.util.ArrayList; class Erase { private List removeLongerThan(List strings, int length) { List result = new ArrayList(); for (int i = 0; i < strings.size(); i++) { String s = (String) strings.get(i); if (s.length() <= length) { result.add(s); } } return result; } public static void main(String[] args) { List names = new ArrayList(); names.add("Ted"); names.add("Fred"); names.add("Jed"); names.add("Ned"); System.out.println(names); Erase e = new Erase(); List shortNames = e.removeLongerThan(names, 3); System.out.println(shortNames.size()); for (int i = 0; i < shortNames.size(); i++) { String s = (String) shortNames.get(i); System.out.println(s); } } } This code is valid Java and valid Groovy Based on an example by Jim Weirich & Ted Leung
  30. 30. ...A Better Java... DSLs 2010 - 30 ©ASERT2006-2010 import java.util.List; import java.util.ArrayList; class Erase { private List removeLongerThan(List strings, int length) { List result = new ArrayList(); for (int i = 0; i < strings.size(); i++) { String s = (String) strings.get(i); if (s.length() <= length) { result.add(s); } } return result; } public static void main(String[] args) { List names = new ArrayList(); names.add("Ted"); names.add("Fred"); names.add("Jed"); names.add("Ned"); System.out.println(names); Erase e = new Erase(); List shortNames = e.removeLongerThan(names, 3); System.out.println(shortNames.size()); for (int i = 0; i < shortNames.size(); i++) { String s = (String) shortNames.get(i); System.out.println(s); } } } Do the semicolons add anything? And shouldn‟t we us more modern list notation? Why not import common libraries?
  31. 31. ...A Better Java... DSLs 2010 - 31 ©ASERT2006-2010 class Erase { private List removeLongerThan(List strings, int length) { List result = new ArrayList() for (String s in strings) { if (s.length() <= length) { result.add(s) } } return result } public static void main(String[] args) { List names = new ArrayList() names.add("Ted"); names.add("Fred") names.add("Jed"); names.add("Ned") System.out.println(names) Erase e = new Erase() List shortNames = e.removeLongerThan(names, 3) System.out.println(shortNames.size()) for (String s in shortNames) { System.out.println(s) } } }
  32. 32. ...A Better Java... DSLs 2010 - 32 ©ASERT2006-2010 class Erase { private List removeLongerThan(List strings, int length) { List result = new ArrayList() for (String s in strings) { if (s.length() <= length) { result.add(s) } } return result } public static void main(String[] args) { List names = new ArrayList() names.add("Ted"); names.add("Fred") names.add("Jed"); names.add("Ned") System.out.println(names) Erase e = new Erase() List shortNames = e.removeLongerThan(names, 3) System.out.println(shortNames.size()) for (String s in shortNames) { System.out.println(s) } } } Do we need the static types? Must we always have a main method and class definition? How about improved consistency?
  33. 33. ...A Better Java... DSLs 2010 - 33 ©ASERT2006-2010 def removeLongerThan(strings, length) { def result = new ArrayList() for (s in strings) { if (s.size() <= length) { result.add(s) } } return result } names = new ArrayList() names.add("Ted") names.add("Fred") names.add("Jed") names.add("Ned") System.out.println(names) shortNames = removeLongerThan(names, 3) System.out.println(shortNames.size()) for (s in shortNames) { System.out.println(s) }
  34. 34. ...A Better Java... DSLs 2010 - 34 ©ASERT2006-2010 def removeLongerThan(strings, length) { def result = new ArrayList() for (s in strings) { if (s.size() <= length) { result.add(s) } } return result } names = new ArrayList() names.add("Ted") names.add("Fred") names.add("Jed") names.add("Ned") System.out.println(names) shortNames = removeLongerThan(names, 3) System.out.println(shortNames.size()) for (s in shortNames) { System.out.println(s) } Shouldn‟t we have special notation for lists? And special facilities for list processing? Is „return‟ needed at end?
  35. 35. ...A Better Java... DSLs 2010 - 35 ©ASERT2006-2010 def removeLongerThan(strings, length) { strings.findAll{ it.size() <= length } } names = ["Ted", "Fred", "Jed", "Ned"] System.out.println(names) shortNames = removeLongerThan(names, 3) System.out.println(shortNames.size()) shortNames.each{ System.out.println(s) }
  36. 36. ...A Better Java... DSLs 2010 - 36 ©ASERT2006-2010 def removeLongerThan(strings, length) { strings.findAll{ it.size() <= length } } names = ["Ted", "Fred", "Jed", "Ned"] System.out.println(names) shortNames = removeLongerThan(names, 3) System.out.println(shortNames.size()) shortNames.each{ System.out.println(s) } Is the method now needed? Easier ways to use common methods? Are brackets required here?
  37. 37. ...A Better Java... DSLs 2010 - 37 ©ASERT2006-2010 names = ["Ted", "Fred", "Jed", "Ned"] println names shortNames = names.findAll{ it.size() <= 3 } println shortNames.size() shortNames.each{ println it }
  38. 38. ...A Better Java DSLs 2010 - 38 ©ASERT2006-2010 names = ["Ted", "Fred", "Jed", "Ned"] println names shortNames = names.findAll{ it.size() <= 3 } println shortNames.size() shortNames.each{ println it } ["Ted", "Fred", "Jed", "Ned"] 3 Ted Jed Ned
  39. 39. Grapes / Grab DSLs 2010 - 39 ©ASERT2006-2010 // Google Collections example @Grab('com.google.collections:google-collections:1.0') import com.google.common.collect.HashBiMap HashBiMap fruit = [grape:'purple', lemon:'yellow', lime:'green'] assert fruit.lemon == 'yellow' assert fruit.inverse().yellow == 'lemon'
  40. 40. Malleable Syntax DSLs 2010 - 40 ©ASERT2006-2010 order to buy 200.shares of GOOG { limitPrice 500 allOrNone false at the value of { qty * unitPrice - 100 } } take 2.pills of chloroquinine after 6.hours Groovy 1.8+ def "length of Spock's & his friends' names"() { expect: name.size() == length where: name | length "Spock" | 5 "Kirk" | 4 "Scotty" | 6 }
  41. 41. 41 Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. Real-life Groovy DSL examples • Anti-malaria drug resistance simulation • Human Resources employee skills representation • Insurance policies risk calculation engine • Loan acceptance rules engine for a financial platform • Mathematica-like lingua for nuclear safety simulations • Market data feeds evolution scenarios • and more...
  42. 42. 42 Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. DSLs within the Groovy Ecosystem • Testing DSLs – EasyB, Spock, JBehave, … • Builders – MarkupBuilder, SwingBuilder • Build Tool DSLs – AntBuilder, Gant, Gradle • Grails – BeanBuilder, Criteria, ConfigSlurper • GPars – DSL for concurrent activities • and more...
  43. 43. Testing DSLs: Spock... ©ASERT2006-2010 DSLs 2010 - 43
  44. 44. ...Testing DSLs: Spock... ©ASERT2006-2010 • Testing framework for Java and Groovy • Highly expressive specification language – No assertion API – No record & replay mocking API – No superfluous annotations – Meaningful assert error messages – Extensible – Compatible with JUnit reportingwise @Speck @RunWith(Sputnik) class PublisherSubscriberSpeck { def "events are received by all subscribers"() { def pub = new Publisher() def sub1 = Mock(Subscriber) def sub2 = Mock(Subscriber) pub.subscribers << sub1 << sub2 when: pub.send("event") then: 1 * sub1.receive("event") 1 * sub2.receive("event") } } DSLs 2010 - 44
  45. 45. ...Testing DSLs: Spock... ©ASERT2006-2010 import com.gargoylesoftware.htmlunit.WebClient import spock.lang.* import org.junit.runner.RunWith @Speck () @RunWith (Sputnik) class TestSimpBlogSpock { def page, subheadings, para, form, result @Unroll("When #author posts a #category blog with content '#content' it sho def "when creating a new blog entry"() { given: page = new WebClient().getPage('http://localhost:8080/postForm') form = page.getFormByName('post') when: form.getInputByName('title').setValueAttribute("$author was here (and s form.getSelectByName('category').getOptions().find { it.text == categor form.getSelectByName('author').getOptions().find { it.text == author }. form.getTextAreaByName('content').setText(content) result = form.getInputByName('btnPost').click() subheadings = result.getElementsByTagName('h3') para = result.getByXPath('//TABLE//TR/TD/P')[0] ... DSLs 2010 - 45
  46. 46. ... Testing DSLs: Spock ©ASERT2006-2010 ... then: page.titleText == 'Welcome to SimpBlog' result.getElementsByTagName('h1').item(0).textContent.matches("Post.*: $au subheadings.item(1).textContent == "Category: $category" subheadings.item(2).textContent == "Author: $author" and: para.textContent == content where: author << ['Bart', 'Homer', 'Lisa'] category << ['Home', 'Work', 'Food'] content << ['foo', 'bar', 'baz'] } } // Optional use of 'and:' DSLs 2010 - 46
  47. 47. ©ASERT2006-2010 Testing DSLs: EasyB… • Description: BDD, Rspec-like testing library narrative 'segment flown', { as_a 'frequent flyer' i_want 'to accrue rewards points for every segment I fly' so_that 'I can receive free flights for my dedication to the airline' } scenario 'segment flown', { given 'a frequent flyer with a rewards balance of 1500 points' when 'that flyer completes a segment worth 500 points' then 'that flyer has a new rewards balance of 2000 points' } scenario 'segment flown', { given 'a frequent flyer with a rewards balance of 1500 points', { flyer = new FrequentFlyer(1500) } when 'that flyer completes a segment worth 500 points', { flyer.fly(new Segment(500)) } then 'that flyer has a new rewards balance of 2000 points', { flyer.pointsBalance.shouldBe 2000 } } DSLs 2010 - 47
  48. 48. …Testing DSLs: EasyB • When run will be marked as pending – perfect for ATDD ©ASERT2006-2010 scenario "Bart posts a new blog entry", { given "we are on the create blog entry page" when "I have entered 'Bart was here' as the title" and "I have entered 'Cowabunga Dude!' into the content" and "I have selected 'Home' as the category" and "I have selected 'Bart' as the author" and "I click the 'Create Post' button" then "I expect the entry to be posted" } DSLs 2010 - 48
  49. 49. Testing DSLS: Cucumber... ©ASERT2006-2010 # language: en @newpost Feature: New Blog Post In order to create a new blog entry Bloggers should be able to select their name and category and enter text Scenario: New Posting Given we are on the create blog entry page When I have entered "Bart was here" as the title And I have entered "Cowabunga Dude!" as the content And I have selected "Home" from the "category" dropdown And I have selected "Bart" from the "author" dropdown And I click the 'Create Post' button Then I should see a heading message matching "Post.*: Bart was here.*" DSLs 2010 - 49
  50. 50. ... Testing DSLS: Cucumber... ©ASERT2006-2010 DSLs 2010 - 50
  51. 51. ...Testing DSLS: Cucumber ©ASERT2006-2010 import com.gargoylesoftware.htmlunit.WebClient this.metaClass.mixin(cuke4duke.GroovyDsl) Given ~/we are on the create blog entry page/, { -> page = new WebClient().getPage('http://localhost:8080/postForm') } When(~/I have entered "(.*)" as the title/) {String title -> form = page.getFormByName('post') form.getInputByName('title').setValueAttribute(title + ' (and so was Cucumber)') } When(~'I have entered "(.*)" as the content') {String content -> form.getTextAreaByName('content').setText(content) } When(~'I have selected "(.*)" from the "(.*)" dropdown') {String option, String name -> form.getSelectByName(name).getOptions().find { it.text == option }.setSelected(true) } When(~"I click the 'Create Post' button") { -> result = form.getInputByName('btnPost').click() } Then(~'I should see a heading message matching "(.*)"') {String pattern -> // ensureThat result.getElementsByTagName('h1').item(0).textContent.matches(pattern) assert result.getElementsByTagName('h1').item(0).textContent.matches(pattern) } DSLs 2010 - 51
  52. 52. Grails Criteria DSLs 2010 - 52 ©ASERT2006-2010 // Account is a POJO in our domain/model def c = Account.createCriteria() def results = c { like("holderFirstName", "Fred%") and { between("balance", 500, 1000) eq("branch", "London") } maxResults(10) order("holderLastName", "desc") } // source: Grails doco: 5. Object Relational Mapping (GORM): 5.4.2 Criteria
  53. 53. Grails Criteria Example DSLs 2010 - 53 ©ASERT2006-2010 // Book is a POJO in our domain/model def book = Book.findByTitle("The Stand") book = Book.findByTitleLike("Harry Pot%") book = Book.findByReleaseDateBetween( firstDate, secondDate ) book = Book.findByReleaseDateGreaterThan( someDate ) book = Book.findByTitleLikeOrReleaseDateLessThan( "%Something%", someDate ) books = Book.findAllByTitleLikeAndReleaseDateGreaterThan( "%Java%", new Date()-30) // source: Grails doco: 5. Object Relational Mapping (GORM): 5.4.1 Dynamic Finders
  54. 54. Grails Bean Builder Example DSLs 2010 - 54 ©ASERT2006-2010 bb.beans { marge(Person) { name = "marge" husband = { Person p -> name = "homer" age = 45 props = [overweight:true, height:"1.8m"] } children = [bart, lisa] } bart(Person) { name = "Bart" age = 11 } lisa(Person) { name = "Lisa" age = 9 } } // source: 14. Grails and Spring: 14.3 Runtime Spring with the Beans DSL
  55. 55. GPars... import static org.gparallelizer.actors.pooledActors.PooledActors.* // create a new actor that prints out received messages def console = actor { loop { react {message -> println message } } } // start the actor and send it a message console.start() console.send('Message') DSLs 2010 - 55
  56. 56. ...GPars import static org.gparallelizer.dataflow.DataFlow.thread final def x = new DataFlowVariable() final def y = new DataFlowVariable() final def z = new DataFlowVariable() thread { z << ~x + ~y println "Result: ${~z}" } thread { x << 10 } thread { y << 5 } No race-conditions No deadlocks No live-locks Completely deterministic programs BEAUTIFUL code DSLs 2010 - 56
  57. 57. Topics • Introduction Groovy DSL Features • A Week In The Life Of DSL INC • Summary • More Info DSLs 2010 - 57 ©ASERT2006-2010
  58. 58. Groovy DSL Features DSLs 2010 - 58 ©ASERT2006-2010
  59. 59. Import / Import Static • Imports • Static Imports DSLs 2010 - 59 ©ASERT2006-2010 @Grab('com.google.collections:google-collections:1.0') import com.google.common.collect.HashBiMap as HashMap def m = new HashMap() m.key = 'value' assert m.inverse().value == 'key' import static java.util.Calendar.getInstance as now println now().format('yyyy/MMM/dd') What Java gives us plus aliases
  60. 60. Static Imports... DSLs 2010 - 60 ©ASERT2006-2010 import groovy.swing.SwingXBuilder import static java.awt.Color.* import static java.lang.Math.* def swing = new SwingXBuilder() def frame = swing.frame(size: [300, 300]) { graph(plots: [ [GREEN, {value -> sin(value)}], [BLUE, {value -> cos(value)}], [RED, {value -> tan(value)}] ]) }.show()  Java Static Imports Discussed later:  Builders  Closures
  61. 61. ...Static Imports... DSLs 2010 - 61 ©ASERT2006-2010 import groovy.swing.SwingXBuilder import static java.awt.Color.* import static java.lang.Math.* def swing = new SwingXBuilder() def frame = swing.frame(size: [300, 300]) { graph(plots: [ [GREEN, {value -> sin(value)}], [BLUE, {value -> cos(value)}], [RED, {value -> tan(value)}] ]) }.show() Java gives us this
  62. 62. ...Static Imports... DSLs 2010 - 62 ©ASERT2006-2010 import groovy.swing.SwingXBuilder import static java.awt.Color.* import static java.lang.Math.* def swing = new SwingXBuilder() def frame = swing.frame(size: [300, 300]) { graph(plots: [ [GREEN, {value -> sin(value)}], [BLUE, {value -> cos(value)}], [RED, {value -> tan(value)}] ]) }.show() Java gives us this
  63. 63. ...Static Imports... DSLs 2010 - 63 ©ASERT2006-2010 Source: http://www.thedoghousediaries.com/?p=1406
  64. 64. ...Static Imports DSLs 2010 - 64 ©ASERT2006-2010 import groovy.swing.SwingXBuilder import static java.lang.Math.* import static java.awt.Color.GREEN as Lime import static java.awt.Color.BLUE as Sky import static java.awt.Color.RED as Maraschino def swing = new SwingXBuilder() def frame = swing.frame(size: [300, 300]) { graph(plots: [ [Lime, {value -> sin(value)}], [Sky, {value -> cos(value)}], [Maraschino, {value -> tan(value)}] ]) }.show() Java doesn‟t give us this!
  65. 65. Literal Syntax Conventions • Lists – Special syntax for list literals – Additional common methods (operator overloading) • Maps – Special syntax for map literals – Additional common methods • Ranges – Special syntax for various kinds of ranges DSLs 2010 - 65 ©ASERT2006-2010 def list = [3, new Date(), 'Jan'] assert list + list == list * 2 def map = [a: 1, b: 2] assert map['a'] == 1 && map.b == 2 def letters = 'a'..'z' def numbers = 0..<10
  66. 66. Literal Syntax Conventions in DSLs DSLs 2010 - 66 ©ASERT2006-2010 import static java.util.Calendar.getInstance as getNow import static java.util.Calendar.* def discount = [normal:0, silver:5, gold:10] def roomrate = [weekday:150, weekend:95] for (level in ['normal', 'silver', 'gold']) { def multiplier = 1 - discount[level] / 100 print 'Your room rate is: ' if (now[DAY_OF_WEEK] in MONDAY..FRIDAY) println roomrate.weekday * multiplier else println roomrate.weekend * multiplier } Your room rate is: 150 Your room rate is: 142.50 Your room rate is: 135.0  Literal list & map syntax  Ranges Also  Static import aliases  BigDecimal arithmetic
  67. 67. Compact Syntax... • Java • Groovy DSLs 2010 - 67 ©ASERT2006-2010 public class BuySharesJava { public static void buyShares(int qty, String name) { // business logic here ... System.out.println("buying " + qty + " shares of " + name); } public static void main(String[] args) { buyShares(3, "BHP"); } } def buyShares(qty, name) { // business logic here ... println "buying $qty shares of $name" } buyShares 3, 'BHP'  Script syntax  Conventions for visibility  GDK methods: println  Implicit typing  GString interpolation  Optional brackets & „;‟
  68. 68. ...Compact Syntax... • Java • Groovy DSLs 2010 - 68 ©ASERT2006-2010 import java.util.Date; import java.util.HashMap; import java.util.Map; public class ProcessCustomerJava { public static void printDetails(Map<String, String> cust) { System.out.println("Details as at: " + new Date()); String first = cust.get("first"); System.out.println("First name: " + first); String last = cust.get("last"); System.out.println("Last name: " + (last != null ? last : "unknown")); } public static void main(String[] args) { Map<String, String> details = new HashMap<String, String>(); details.put("first", "John"); details.put("last", "Smith"); printDetails(details); } } def printDetails(cust) { println """Details as at: ${new Date()} First name: $cust.first Last name: ${cust.last ?: 'unknown'}""" } printDetails first: 'John', last: 'Smith'  Script syntax, Named params, Extra imports  Conventions for visibility, GDK methods  Implicit typing, Multi-line GString  Elvis operator, Optional brackets & „;‟
  69. 69. ...Compact Syntax • Java • Groovy DSLs 2010 - 69 ©ASERT2006-2010 import java.util.Date; public class ProcessStrongCustomerJava { public static void printDetails(CustomerJ cust) { System.out.println("Details as at: " + new Date()); String first = cust.getFirst(); System.out.println("First name: " + first); String last = cust.getLast(); System.out.println("Last name: " + (last != null ? last : "unknown")); } public static void main(String[] args) { CustomerJ c = new CustomerJ(); c.setFirst("John"); c.setLast("Smith"); printDetails(c); } } class CustomerJ { private String first; private String last; public String getFirst() { return first; } public void setFirst(String first) { this.first = first; } public String getLast() { return last; } public void setLast(String last) { this.last = last; } } class CustomerG { String first, last } def printDetails(cust) { println """Details as at: ${new Date()} First name: $cust.first Last name: ${cust.last ?: 'unknown'}""" } printDetails new CustomerG(first: 'John', last: 'Smith') Plus:  Named params for constructors  JavaBean conventions  Leverage Duck Typing
  70. 70. Using With Example DSLs 2010 - 70 ©ASERT2006-2010 letters = ['a', 'b', 'c'] range = 'b'..'d' letters.with { add 'd' remove 'a' } assert letters == range map = [a:10, b:4, c:7] map.with { assert (a + b) / c == 2 } Just normal methods for ArrayList here
  71. 71. Closures... • Traditional mainstream languages – Data can be stored in variables, passed around, combined in structured ways to form more complex data; code stays put where it is defined • Languages supporting closures – Data and code can be stored in variables, passed around, combined in structured ways to form more complex algorithms and data; functional coding style DSLs 2010 - 71 ©ASERT2006-2010 doubleNum = { num -> num * 2 } println doubleNum(3) // => 6 processThenPrint = { num, closure -> num = closure(num); println "num is $num" } processThenPrint(3, doubleNum) // => num is 6 processThenPrint(10) { it / 2 } // => num is 5
  72. 72. ...Closures... DSLs 2010 - 72 ©ASERT2006-2010 int myConst = 4 def multiplier = { number -> number * myConst } assert multiplier(10) == 40 Closure other = { it + myConst } assert other.call(10) == 14 def twice = { it * 2 } // anonymous functions assert twice(10) == 20 // implemented as Closures Name
  73. 73. ...Closures... DSLs 2010 - 73 ©ASERT2006-2010 int myConst = 4 def multiplier = { number -> number * myConst } assert multiplier(10) == 40 Closure other = { it + myConst } assert other.call(10) == 14 def twice = { it * 2 } // anonymous functions assert twice(10) == 20 // implemented as Closures Code
  74. 74. ...Closures... DSLs 2010 - 74 ©ASERT2006-2010 int myConst = 4 def multiplier = { number -> number * myConst } assert multiplier(10) == 40 Closure other = { it + myConst } assert other.call(10) == 14 def twice = { it * 2 } // anonymous functions assert twice(10) == 20 // implemented as Closures Parameter(s) Default parameter
  75. 75. ...Closures... DSLs 2010 - 75 ©ASERT2006-2010 int myConst = 4 def multiplier = { number -> number * myConst } assert multiplier(10) == 40 Closure other = { it + myConst } assert other.call(10) == 14 def twice = { it * 2 } // anonymous functions assert twice(10) == 20 // implemented as Closures Call closure Alternative syntax
  76. 76. ...Closures... DSLs 2010 - 76 ©ASERT2006-2010 int myConst = 4 def multiplier = { number -> number * myConst } assert multiplier(10) == 40 Closure other = { it + myConst } assert other.call(10) == 14 def twice = { it * 2 } // anonymous functions assert twice(10) == 20 // implemented as Closures Free variable
  77. 77. ...Closures... DSLs 2010 - 77 ©ASERT2006-2010 int myConst = 4 def multiplier = { number -> number * myConst } assert multiplier(10) == 40 Closure other = { it + myConst } assert other.call(10) == 14 def twice = { it * 2 } // anonymous functions assert twice(10) == 20 // implemented as Closures Bound to environment/context when called
  78. 78. Closures in DSLs... DSLs 2010 - 78 ©ASERT2006-2010 import static java.util.Calendar.* def cart1 = [ [qty: 3, unitPrice: 50.0, gift: true, name: 'Groovy in Action Book'], [qty: 1, unitPrice: 40.0, gift: false, name: 'Grails in Action eBook'], [qty: 2, unitPrice: 25.0, gift: true, name: 'Avatar DVD'] ] def cart2 = [ [qty: 1, unitPrice: 50.0, gift: true, name: 'Groovy in Action Book'], [qty: 2, unitPrice: 30.0, gift: false, name: 'Avatar 3D DVD'] ] // ... Nothing special here. Just a list of maps.
  79. 79. ... Closures in DSLs... DSLs 2010 - 79 ©ASERT2006-2010 // ... def noDiscount = { it.unitPrice * it.qty } def tenPercentOffAll = { it.unitPrice * it.qty * 0.9 } def tenPercentOffGifts = { it.with { unitPrice * qty * (gift ? 0.9 : 1.0) } } def tenPercentOffOverForty = { it.with { unitPrice * qty * (unitPrice > 40 ? 0.9 : 1.0) } } def tenPercentOffBooks = { it.with { unitPrice * qty * (name.contains('Book') ? 0.9 : 1.0) } } def tenPercentOffDVDs = { it.with { unitPrice * qty * (name.contains('DVD') ? 0.9 : 1.0) } } def buyThreeGetOneFree = { it.with { unitPrice * (qty % 3 + 2 * qty.intdiv(3)) } } // ... Closure Name
  80. 80. ... Closures in DSLs... DSLs 2010 - 80 ©ASERT2006-2010 // ... def noDiscount = { it.unitPrice * it.qty } def tenPercentOffAll = { it.unitPrice * it.qty * 0.9 } def tenPercentOffGifts = { it.with { unitPrice * qty * (gift ? 0.9 : 1.0) } } def tenPercentOffOverForty = { it.with { unitPrice * qty * (unitPrice > 40 ? 0.9 : 1.0) } } def tenPercentOffBooks = { it.with { unitPrice * qty * (name.contains('Book') ? 0.9 : 1.0) } } def tenPercentOffDVDs = { it.with { unitPrice * qty * (name.contains('DVD') ? 0.9 : 1.0) } } def buyThreeGetOneFree = { it.with { unitPrice * (qty % 3 + 2 * qty.intdiv(3)) } } // ... Closure Code
  81. 81. ... Closures in DSLs DSLs 2010 - 81 ©ASERT2006-2010 // ... def specials = [noDiscount, tenPercentOffAll, tenPercentOffGifts, tenPercentOffOverForty, tenPercentOffBooks, tenPercentOffDVDs, buyThreeGetOneFree] [ SUNDAY..SATURDAY, [cart1, cart2] ].combinations().each { day, cart -> printf "%d %2.2fn", day, cart.sum(specials[day-1]) } 1 240.00 2 216.00 3 220.00 4 225.00 5 221.00 6 235.00 7 190.00 1 110.00 2 99.00 3 105.00 4 105.00 5 105.00 6 104.00 7 110.00
  82. 82. Operator Overloading Example DSLs 2010 - 82 ©ASERT2006-2010 BigDecimal a = new BigDecimal(3.5d); BigDecimal b = new BigDecimal(4.0d); assert a.multiply(b).compareTo(new BigDecimal(14.0d)) == 0; assert a.multiply(b).equals(new BigDecimal(14.0d).setScale(1)); def c = 3.5, d = 4.0 assert c * d == 14.0 • Java • Groovy
  83. 83. Groovy Lab Example DSLs 2010 - 83 ©ASERT2006-2010 // require GroovyLab import static org.math.array.Matrix.* import static org.math.plot.Plot.* def A = rand(10,3) // random Matrix of 10 rows and 3 columns def B = fill(10,3,1.0) // one Matrix of 10 rows and 3 columns def C = A + B // support for matrix addition with "+" or "-" def D = A - 2.0 // support for number addition with "+" or "-" def E = A * B // support for matrix multiplication or division def F = rand(3,3) def G = F**(-1) // support for matrix power (with integers only) println A // display Matrix content plot("A",A,"SCATTER") // plot Matrix values as ScatterPlot def M = rand(5,5) + id(5) // Eigenvalues decomposition println "M=n" + M println "V=n" + V(M) println "D=n" + D(M) println "M~n" + (V(M) * D(M) * V(M)**(-1))
  84. 84. ©ASERT2006-2010 Better Control Structures: Switch Poker… suits = 'SHDC' ranks = '23456789TJQKA' suit = { String card -> suits.indexOf(card[1]) } rank = { String card -> ranks.indexOf(card[0]) } rankSizes = { List cards -> cards.groupBy(rank).collect{ k, v -> v.size() }.sort() } rankValues = { List cards -> cards.collect{ rank(it) }.sort() } // ... 8C TS KC 9H 4S 7D 2S 5D 3S AC hand1 hand2 println rankSizes(["7S", "7H", "2H", "7D", "AH"]) // => [1, 1, 3] DSLs 2010 - 84
  85. 85. ©ASERT2006-2010 …Better Control Structures: Switch Poker… // ... flush = { List cards -> cards.groupBy(suit).size() == 1 } straight = { def v = rankValues(it); v == v[0]..v[0]+4 } straightFlush = { List cards -> straight(cards) && flush(cards) } fourOfAKind = { List cards -> rankSizes(cards) == [1, 4] } fullHouse = { List cards -> rankSizes(cards) == [2, 3] } threeOfAKind = { List cards -> rankSizes(cards) == [1, 1, 3] } twoPair = { List cards -> rankSizes(cards) == [1, 2, 2] } pair = { List cards -> rankSizes(cards) == [1, 1, 1, 2] } // ... DSLs 2010 - 85
  86. 86. ©ASERT2006-2010 … Better Control Structures: Switch Poker // ... def rankHand(List cards) { switch (cards) { case straightFlush : return 9 case fourOfAKind : return 8 case fullHouse : return 7 case flush : return 6 case straight : return 5 case threeOfAKind : return 4 case twoPair : return 3 case pair : return 2 default : return 1 } } // ... DSLs 2010 - 86
  87. 87. Type Transformation Example DSLs 2010 - 87 ©ASERT2006-2010 class InventoryItem { def weight, name InventoryItem(Map m) { this.weight = m.weight; this.name = m.name } InventoryItem(weight, name) { this.weight = weight; this.name = name } InventoryItem(String s) { s.find(/weight=(d*)/) { all, w -> this.weight = w } s.find(/name=(.*)/) { all, n -> this.name = n } } } def room = [:] def gold = [weight:50, name:'Gold'] as InventoryItem def emerald = [10, 'Emerald'] as InventoryItem def dagger = ['weight=5, name=Dagger'] as InventoryItem room.contents = [gold, emerald, dagger] room.contents.each{ println it.dump() }
  88. 88. DSLs 2010 - 88 Groovy DSL Features ©ASERT2006-2010
  89. 89. Metaprogramming • Runtime Metaprogramming – Categories including DGM – invokeMethod, methodMissing, getProperty – GroovyInterceptable – ExpandoMetaClass DSLs 2010 - 89 ©ASERT2006-2010
  90. 90. DSLs 2010 - 90 ©ASERT2006-2010 Builders… <html> <head> <title>Hello</title> </head> <body> <ul> <li>world 1</li> <li>world 2</li> <li>world 3</li> <li>world 4</li> <li>world 5</li> </ul> </body> </html> import groovy.xml.* def page = new MarkupBuilder() page.html { head { title 'Hello' } body { ul { for (count in 1..5) { li "world $count" } } } } • MarkupBuilder
  91. 91. ...Builders… DSLs 2010 - 91 ©ASERT2006-2010 def colors = ['red','darkOrange','blue','darkGreen'] (0..3).each { index -> star( cx: 50 + (index*110), cy: 50, or: 40, ir: 15, borderColor: 'black', count: 2+index, fill: colors[index] ) star( cx: 50 + (index*110), cy: 140, or: 40, ir: 15, borderColor: 'black‘, count: 7+index, fill: colors[index] ) } • GraphicsBuilder
  92. 92. …Builders new AntBuilder().with { echo(file:'Temp.java', ''' class Temp { public static void main(String[] args) { System.out.println("Hello"); } } ''') javac(srcdir:'.', includes:'Temp.java', fork:'true') java(classpath:'.', classname:'Temp', fork:'true') echo('Done') } // => // [javac] Compiling 1 source file // [java] Hello // [echo] Done ©ASERT2006-2010 DSLs 2010 - 92
  93. 93. 93 Copyright 2010 SpringSource. Copying, publishing or distributing without express written permission is prohibited. A builder for HR
  94. 94. DSLs 2010 - 94 ©ASERT2006-2010 ExpandoMetaClass… import static java.lang.Character.isUpperCase String.metaClass.swapCase = { delegate.collect { ch -> isUpperCase(ch as char) ? ch.toLowerCase() : ch.toUpperCase() }.join() } println new Date().toString().swapCase() // => sUN nOV 09 17:30:06 est 2008 List.metaClass.sizeDoubled = {-> delegate.size() * 2 } LinkedList list = [] list << 1 list << 2 assert 4 == list.sizeDoubled()
  95. 95. DSLs 2010 - 95 ©ASERT2006-2010 …ExpandoMetaClass class Person { String name } class MortgageLender { def borrowMoney() { "buy house" } } def lender = new MortgageLender() Person.metaClass.buyHouse = lender.&borrowMoney def p = new Person() assert "buy house" == p.buyHouse()
  96. 96. Adding your own control structures • Thread enhancement DSLs 2010 - 96 ROCK! . 25 . 33 . 34 . 35 . 36 .. 131 .. 134 .. 137 .. 138 .. 139 ... 232 ... 234 ... 237 ... 238 ... 239 .... 334 .... 336 .... 337 .... 338 .... 339 import java.util.concurrent.locks.ReentrantLock import static System.currentTimeMillis as now def startTime = now() ReentrantLock.metaClass.withLock = { critical -> lock() try { critical() } finally { unlock() } } def lock = new ReentrantLock() def worker = { threadNum -> 4.times { count -> lock.withLock { print " " * threadNum print "." * (count + 1) println " ${now() - startTime}" } Thread.sleep 100 } } 5.times { Thread.start worker.curry(it) } println "ROCK!" Source: http://chrisbroadfoot.id.au/articles/2008/08/06/groovy-threads
  97. 97. EMC DSL… DSLs 2010 - 97 ©ASERT2006-2010
  98. 98. ...EMC Neo4j DSL… DSLs 2010 - 98 ©ASERT2006-2010 @GrabResolver(name= 'neo4j-public-repo', root= 'http://m2.neo4j.org') @Grab('org.neo4j:neo4j-kernel:1.1.1') import org.neo4j.kernel.EmbeddedGraphDatabase import org.neo4j.graphdb.* // an enum helper enum MyRelationships implements RelationshipType { knows } // some optional syntactic sugar using EMC DSL Node.metaClass { propertyMissing { String name, val -> delegate.setProperty(name, val) } propertyMissing { String name -> delegate.getProperty(name) } methodMissing { String name, args -> delegate.createRelationshipTo(args[0], MyRelationships."$name") } } Relationship.metaClass { propertyMissing { String name, val -> delegate.setProperty(name, val) } propertyMissing { String name -> delegate.getProperty(name) } } // ...
  99. 99. …EMC Neo4j DSL DSLs 2010 - 99 ©ASERT2006-2010 // ... def graphDb = new EmbeddedGraphDatabase("graphdb") def tx = graphDb.beginTx() def firstNode, secondNode, relationship try { firstNode = graphDb.createNode() secondNode = graphDb.createNode() relationship = firstNode.knows(secondNode) firstNode.message = "Hello," secondNode.message = "world!" relationship.message = "brave Neo4j" tx.success() } finally { tx.finish() println "$firstNode.message $relationship.message $secondNode.message" // => Hello, brave Neo4j world! graphDb.shutdown() }
  100. 100. Game example... DSLs 2010 - 100 ©ASERT2006-2010 // Trying out the game DSL idea by Sten Anderson from: // http://blogs.citytechinc.com/sanderson/?p=92 class GameUtils { static VOWELS = ['a', 'e', 'i', 'o', 'u'] static listItems(things) { def result = '' things.eachWithIndex{ thing, index -> if (index > 0) { if (index == things.size() - 1) result += ' and ' else if (index < things.size() - 1) result += ', ' } result += "${thing.toLowerCase()[0] in VOWELS ? 'an' : 'a'} $thing } result ?: 'nothing' } } import static GameUtils.* ...
  101. 101. ...Game example... DSLs 2010 - 101 ©ASERT2006-2010 ... class Room { def description def contents = [] } ...
  102. 102. ...Game example... DSLs 2010 - 102 ©ASERT2006-2010 ... class Player { def currentRoom def inventory = [] void look() { println "You are in ${currentRoom?.description?:'the void'} which contains ${listItems(currentRoom?.contents)}" } void inv() { println "You are holding ${listItems(inventory)}" } void take(item) { if (currentRoom?.contents?.remove(item)) { inventory << item println "You took the $item" } else { println "I see no $item here" } } ...
  103. 103. ...Game example... DSLs 2010 - 103 ©ASERT2006-2010 ... void drop(item) { if (inventory?.remove(item)) { currentRoom?.contents << item println "You dropped the $item" } else { println "You don't have the $item" } } def propertyMissing(String name) { if (metaClass.respondsTo(this, name)) { this."$name"() } name } } ...
  104. 104. ...Game example... DSLs 2010 - 104 ©ASERT2006-2010 ... Room plainRoom = new Room(description:'a plain white room', contents:['dagger', 'emerald', 'key']) Player player = new Player(currentRoom:plainRoom) player.with { inv look take dagger inv look take emerald inv look take key drop emerald inv look } assert player.inventory == ['dagger', 'key'] ...
  105. 105. ...Game example DSLs 2010 - 105 ©ASERT2006-2010 ... // now try some error conditions plainRoom.description = null player.with { drop gold take gold drop emerald take emerald take emerald look }
  106. 106. GEP3 example... DSLs 2010 - 106 ©ASERT2006-2010 Object.metaClass.please = { clos -> clos(delegate) } Object.metaClass.the = { clos -> delegate[1](clos(delegate[0])) } show = { thing -> [thing, { println it }] } square_root = { Math.sqrt(it) } given = { it } given 100 please show the square_root // ==> 10.0
  107. 107. ...GEP3 example... DSLs 2010 - 107 ©ASERT2006-2010 Object.metaClass.of = { delegate[0](delegate[1](it)) } Object.metaClass.the = { clos -> [delegate[0], clos] } show = [{ println it }] square_root = { Math.sqrt(it) } please = { it } please show the square_root of 100 // ==> 10.0
  108. 108. ...GEP3 example... DSLs 2010 - 108 ©ASERT2006-2010 show = { println it } square_root = { Math.sqrt(it) } def please(action) { [the: { what -> [of: { n -> action(what(n)) }] }] } please show the square_root of 100 // ==> 10.0 Inspiration for this example came from …
  109. 109. ...GEP3 example... DSLs 2010 - 109 ©ASERT2006-2010 // Japanese DSL using GEP3 rules Object.metaClass.を = Object.metaClass.の = { clos -> clos(delegate) } まず = { it } 表示する = { println it } 平方根 = { Math.sqrt(it) } まず 100 の 平方根 を 表示する // First, show the square root of 100 // => 10.0 // source: http://d.hatena.ne.jp/uehaj/20100919/1284906117 // http://groovyconsole.appspot.com/edit/241001
  110. 110. ...GEP3 example DSLs 2010 - 110 ©ASERT2006-2010 // source: http://d.hatena.ne.jp/uehaj/20100919/1284906117 // http://groovyconsole.appspot.com/edit/241001
  111. 111. Medical Prescription DSL… DSLs 2010 - 111 ©ASERT2006-2010 class Drug { String name String toString() { name } } class Measure { Number number String unit, units String toString() { number == 1 ? "1 $unit" : "$number $units" } } class Quantity extends Measure {} class Duration extends Measure {} // ... http://groovyconsole.appspot.com/script/240001 by glaforge/Mihai Cazacu
  112. 112. …Medical Prescription DSL… DSLs 2010 - 112 ©ASERT2006-2010 // ... // ---- DSL implementation ------------------------------ Integer.metaClass.getHour = {-> 1.hours } Integer.metaClass.getPill = {-> 1.pills } Integer.metaClass.getHours = {-> new Duration(number: delegate, unit: 'hour', units: 'hours') } Integer.metaClass.getPills = {-> new Quantity(number: delegate, unit: 'pill', units: 'pills') } // use the script binding for storing new drugs available as variables binding = new Binding() { def getVariable(String drug) { new Drug(name: drug) } } take = {Quantity quantity -> ['of': {Drug drug -> ['after': {Duration duration -> println "Take $quantity of $drug afer $duration" }] }] } // ...
  113. 113. …Medical Prescription DSL DSLs 2010 - 113 ©ASERT2006-2010 // ... // ---- DSL ------------------------------- take 2.pills of chloroquinine after 6.hours http://groovyconsole.appspot.com/script/240001 by glaforge/Mihai Cazacu
  114. 114. Groovy DSL Features DSLs 2010 - 114 ©ASERT2006-2010 Transformation
  115. 115. AST Transformations • With metaprogramming, Groovy‟s able to modify the behaviour of programs... at runtime • AST Transformations provide a compile- time approach to modify programs – AST: Abstract Syntax Tree – Ability to change what‟s being compiled at compile- time! • No runtime impact! • Lets you change the semantics of your programs! • Nice way of implementing patterns and removing boiler-plate technical code • Two kinds of transformations: global & local DSLs 2010 - 115
  116. 116. Better Design Patterns: Immutable... • Java Immutable Class – As per Joshua Bloch Effective Java DSLs 2010 - 116 ©ASERT2006-2010 public final class Punter { private final String first; private final String last; public String getFirst() { return first; } public String getLast() { return last; } @Override public int hashCode() { final int prime = 31; int result = 1; result = prime * result + ((first == null) ? 0 : first.hashCode()); result = prime * result + ((last == null) ? 0 : last.hashCode()); return result; } public Punter(String first, String last) { this.first = first; this.last = last; } // ... // ... @Override public boolean equals(Object obj) { if (this == obj) return true; if (obj == null) return false; if (getClass() != obj.getClass()) return false; Punter other = (Punter) obj; if (first == null) { if (other.first != null) return false; } else if (!first.equals(other.first)) return false; if (last == null) { if (other.last != null) return false; } else if (!last.equals(other.last)) return false; return true; } @Override public String toString() { return "Punter(first:" + first + ", last:" + last + ")"; } }
  117. 117. ...Better Design Patterns: Immutable... • Java Immutable Class – As per Joshua Bloch Effective Java DSLs 2010 - 117 ©ASERT2006-2010 public final class Punter { private final String first; private final String last; public String getFirst() { return first; } public String getLast() { return last; } @Override public int hashCode() { final int prime = 31; int result = 1; result = prime * result + ((first == null) ? 0 : first.hashCode()); result = prime * result + ((last == null) ? 0 : last.hashCode()); return result; } public Punter(String first, String last) { this.first = first; this.last = last; } // ... // ... @Override public boolean equals(Object obj) { if (this == obj) return true; if (obj == null) return false; if (getClass() != obj.getClass()) return false; Punter other = (Punter) obj; if (first == null) { if (other.first != null) return false; } else if (!first.equals(other.first)) return false; if (last == null) { if (other.last != null) return false; } else if (!last.equals(other.last)) return false; return true; } @Override public String toString() { return "Punter(first:" + first + ", last:" + last + ")"; } } boilerplate
  118. 118. ...Better Design Patterns: Immutable DSLs 2010 - 118 ©ASERT2006-2010 @Immutable class Punter { String first, last }
  119. 119. Spock DSLs 2010 - 119 ©ASERT2006-2010 def "length of Spock's & his friends' names"() { expect: name.size() == length where: name | length "Spock" | 5 "Kirk" | 4 "Scotty" | 6 }
  120. 120. AST Builder • Numerous approaches, still evolving. “From code” approach: • Produces: def result = new AstBuilder().buildFromCode { println "Hello World" } BlockStatement -> ReturnStatement -> MethodCallExpression -> VariableExpression("this") -> ConstantExpression("println") -> ArgumentListExpression -> ConstantExpression("Hello World") DSLs 2010 - 120
  121. 121. ©ASERT2006-2010 EasyB… • Description: BDD, Rspec-like testing library narrative 'segment flown', { as_a 'frequent flyer' i_want 'to accrue rewards points for every segment I fly' so_that 'I can receive free flights for my dedication to the airline' } scenario 'segment flown', { given 'a frequent flyer with a rewards balance of 1500 points' when 'that flyer completes a segment worth 500 points' then 'that flyer has a new rewards balance of 2000 points' } scenario 'segment flown', { given 'a frequent flyer with a rewards balance of 1500 points', { flyer = new FrequentFlyer(1500) } when 'that flyer completes a segment worth 500 points', { flyer.fly(new Segment(500)) } then 'that flyer has a new rewards balance of 2000 points', { flyer.pointsBalance.shouldBe 2000 } } DSLs 2010 - 121
  122. 122. ©ASERT2006-2010 …EasyB • Description: BDD, Rspec-like testing library examples "The number #{number}' should be converted to #{romanNumerals}", { number = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] romanNumerals = ["I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX", "X"] } scenario "Converting #number into the roman numeral #romanNumerals", { given "the number #number", { theNumber = number } when "the system converts this number to the roman numeral equivalent", { theConvertedNumber = RomanNumerals.fromInteger(theNumber) } then "the result should be #romanNumerals", { theConvertedNumber.shouldBe romanNumerals } } DSLs 2010 - 122 Source: http://www.wakaleo.com/blog/285-example-driven-testing-with-easyb
  123. 123. EasyB Preprocessing... • EasyB supports either of these: • But we would like this: given ("some data") { println '... setting expectations' } Source: http://hamletdarcy.blogspot.com/2010/02/groovy-antlr-plugins-for-better-dsls.html given "some data", { println '... setting expectations' } given "some data" { println '... setting expectations' } DSLs 2010 - 123 But also consider Command Expressions (GEP-3) for Groovy1.8+.
  124. 124. ...EasyB Preprocessing... String addCommas(text) { def pattern = ~/(.*)(given|when|then) "([^"]*(.[^"]*)*)" {(.*)/ def replacement = /$1$2 "$3", {$4/ (text =~ pattern).replaceAll(replacement) } Source: http://hamletdarcy.blogspot.com/2010/02/groovy-antlr-plugins-for-better-dsls.html DSLs 2010 - 124 Adds the comma in where required before Groovy sees it.
  125. 125. ...EasyB Preprocessing class SourceModifierParserPlugin extends AntlrParserPlugin { Reduction parseCST(SourceUnit sourceUnit, Reader reader) throws CompilationFailedException { def text = addCommas(reader.text) StringReader stringReader = new StringReader(text) super.parseCST(sourceUnit, stringReader) } } def parserPluginFactory = new ParserPluginFactory() { ParserPlugin createParserPlugin() { new SourceModifierParserPlugin() } } def conf = new CompilerConfiguration(pluginFactory: parserPluginFactory) def binding = ... def shell = new GroovyShell(binding, conf) Source: http://hamletdarcy.blogspot.com/2010/02/groovy-antlr-plugins-for-better-dsls.html DSLs 2010 - 125 But use with restraint as error messages will be with respect to converted source code not original.
  126. 126. GParsec... • Miniature parsers • Parser Combinators def isLetter = { ch -> return Character.isLetter(ch) } def isDigit = { ch -> return Character.isDigit(ch) } def letter = satisfyC(isLetter) def digit = satisfyC(isDigit) def letterAndDigit = seqC(letter, digit) assert letterAndDigit('a123###') == ['a', '1'] def identifier = seqC(identifierStart, noneOrMoreC(identifierRest)) DSLs 2010 - 126
  127. 127. ...GParsec... • BNF • Groovy definitions variableDeclarator : identifier ( '=' expression )? variableDefinitions : variableDeclarator ( ',' variableDeclarator)* def variableDeclarator = seqC(identifier, optionalC(seqC(assign, expression))) def variableDefinitions = seqC(variableDeclarator, noneOrMoreC(seqC(comma, variableDeclarator))) DSLs 2010 - 127
  128. 128. ...GParsec • satisfyC: combinator consumes a single input when its predicate succeeds • altC (alt3C, altCs): is the choice combinator. Given two parsers it only looks at its second alternative if the first has not consumed any input - regardless of the final value • seqC (seq3C, seqCs): is the sequencing combinator. It runs two parsers in succession and if successful, returns the result of the two parsers • noneOrMoreC, oneOrMoreC: applies a parser zero or more times to an input stream. The result from each application of the parser are returned in a list • optionalC: The combinator optionalC may succeed in parsing some input. It always returns success. DSLs 2010 - 128
  129. 129. Using External Parsers DSLs 2010 - 129 ©ASERT2006-2010 import static com.mdimension.jchronic.Chronic.parse def span = parse("tomorrow at 5pm") println span.endCalendar.format('yyyy-MM-dd HH:mm') // => 2010-05-19 17:00
  130. 130. Topics • Introduction • Groovy DSL Features A Week In The Life Of DSL INC • Summary • More Info DSLs 2010 - 130 ©ASERT2006-2010
  131. 131. MONDAY DSLs 2010 - 131 ©ASERT2006-2010
  132. 132. Currency DSL… DSLs 2010 - 132 ©ASERT2006-2010 From: customer@acme.org To: Guillaume Subject: Project Request Dear Guillaume, We would like a DSL for capturing currency expressions. Just US currency to start with. Thanks, Happy Customer
  133. 133. …Currency DSL... DSLs 2010 - 133 ©ASERT2006-2010 enum Coin { penny(1), nickel(5), dime(10), quarter(25) Coin(int value) { this.value = value } int value } import static Coin.* assert 2 * quarter.value + 1 * nickel.value + 2 * penny.value == 57
  134. 134. …Currency DSL… DSLs 2010 - 134 ©ASERT2006-2010 From: customer@acme.org To: Guillaume Subject: Project Request Dear Guillaume, That works fairly well but can we get rid of the ‘.value’ part of those expressions. They are confusing our users. Thanks, Happy Customer
  135. 135. ...Currency DSL... DSLs 2010 - 135 ©ASERT2006-2010 class CoinMath { static multiply(Integer self, Coin c) { self * c.value } } use (CoinMath) { assert 2 * quarter + 1 * nickel + 2 * penny == 57 } // EMC equivalent Integer.metaClass.multiply = { Coin c -> delegate * c.value } assert 2 * quarter + 1 * nickel + 2 * penny == 57
  136. 136. …Currency DSL… DSLs 2010 - 136 ©ASERT2006-2010 From: customer@acme.org To: Guillaume Subject: Project Request Dear Guillaume, Much better but our users are sometimes using plural as well as singular expressions. Is there anything that you can do about that? Thanks, Happy Customer
  137. 137. ... Currency DSL DSLs 2010 - 137 ©ASERT2006-2010 class CoinValues { static get(Integer self, String name) { self * Coin."${singular(name)}".value } static singular(String val) { val.endsWith('ies') ? val[0..-4] + 'y' : val.endsWith('s') ? val[0..-2] : val } } use (CoinValues) { assert 2.quarters + 1.nickel + 2.pennies == 57 } // EMC equivalent Integer.metaClass.getProperty = { String name -> def mp = Integer.metaClass.getMetaProperty(name) if (mp) return mp.getProperty(delegate) def singular = name.endsWith('ies') ? name[0..-4] + 'y' : name.endsWith('s') ? name[0..-2] : name delegate * Coin."$singular".value } assert 2.quarters + 1.nickel + 2.pennies == 57
  138. 138. TUESDAY DSLs 2010 - 138 ©ASERT2006-2010 http://www.google.com/imgres?imgurl=http://i733.photobucket.com/albums/ww336/snake1953/Day_of_Week/Tue/HappyTuesda
  139. 139. Business logic DSL… DSLs 2010 - 139 ©ASERT2006-2010 From: customer@acme.org To: Paul King Subject: Project Request Dear Paul, Could you please create us a small DSL for capturing our business rules. We are thinking of something like: price = 3 quantity = 10 total = price * quantity Perhaps also an ability to check values: assert total == 30 Thanks, Happy Customer P.S. Will send a couple of more details in a follow-up email but please consider the requirements as being pretty much locked down.
  140. 140. …Business logic DSL… • Options – Embedded Groovy – Regex parser – Antlr parser – Split / StringTokenizer – Parser combinators • … Many options, details not important … DSLs 2010 - 140 ©ASERT2006-2010
  141. 141. … Business logic DSL … DSLs 2010 - 141 ©ASERT2006-2010 From: customer@acme.org To: Paul King Subject: Project Request Date: Mid morning Dear Paul, We were thinking a bit more about it, and it would be good to have just a few more features. Hopefully, they won’t have much impact on your existing design and can be added very quickly. It isn’t much, just the ability to have IF, THEN, ELSE like structures, oh yeah and the ability to have loops, and store stuff in files and get stuff from databases and web services if we need. Thanks, Happy Customer P.S. It would be great if you can be finished by this afternoon. We have a customer who would like this feature RSN. Thanks.
  142. 142. … Business logic DSL … DSLs 2010 - 142 ©ASERT2006-2010 def shell = new GroovyShell() shell.evaluate(''' price = 3 quantity = 10 total = price * quantity assert total == 30 ''')
  143. 143. … Business logic DSL … DSLs 2010 - 143 ©ASERT2006-2010 From: customer@acme.org To: Paul King Subject: Project Request Date: This afternoon Dear Paul, We were really happy with the DSL engine you provided us with but people started importing all sorts of classes. Can you stop them from doing that? Maybe just java.lang.Math only. Also we decided we don’t like ‚while‛ loops anymore. Leave you to it. Thanks, Happy Customer P.S. Have a beer and crab dinner for me at the conference. Bye.
  144. 144. … Business logic DSL … DSLs 2010 - 144 ©ASERT2006-2010 class CustomerShell { Object evaluate(String text) { try { def loader = new CustomerClassLoader() def clazz = loader.parseClass(text) def script = clazz.newInstance() return script.run() } catch (...) { ... } } } class CustomerClassLoader extends GroovyClassLoader { def createCompilationUnit(CompilerConfiguration config, CodeSource codeSource) { CompilationUnit cu = super.createCompilationUnit(config, codeSource) cu.addPhaseOperation(new CustomerFilteringNodeOperation(), Phases.SEMANTIC_ANALYSIS) return cu } } private class CustomerFilteringNodeOperation extends PrimaryClassNodeOperation { // ... private static final allowedStaticImports = [Math].asImmutable() void visitStaticMethodCallExpression(StaticMethodCallExpression smce) { if (!allowedStaticImports.contains(smce.ownerType.getTypeClass())) { throw new SecurityException("Static method call expressions forbidden in acme shell.") } } void visitWhileLoop(WhileStatement whileStatement) { throw new SecurityException("While statements forbidden in acme shell.") } // ... } Please also see the ArithmeticShell which is included under examples in the Groovy distribution
  145. 145. … Business logic DSL DSLs 2010 - 145 ©ASERT2006-2010 def shell = new CustomerShell() shell.evaluate(''' price = 3 quantity = 10 total = price * quantity assert total == 30 ''')
  146. 146. WEDNESDAY DSLs 2010 - 146 ©ASERT2006-2010 http://www.crystalscomments.com/1/days/wednesday/animals/006.jpg
  147. 147. Stock Exchange Order DSL… DSLs 2010 - 147 ©ASERT2006-2010 Example inspired from DSLs in Action: http://www.manning.com/ghosh/ From: customer@finance-broker.org To: Guillaume Subject: Project Request Date: Wednesday morning Dear Guillaume, For our order processing system we have a need to capture client orders using a DSL. An order includes the name of the security to be transacted (buy or sell) as well as quantity and unit price details to specify any constraint that the counterparty would like to impose on the price of transaction. Thanks, Happy Customer
  148. 148. … Stock Exchange Order DSL… DSLs 2010 - 148 ©ASERT2006-2010 // ----- Implementation of the Fluent API ----- enum Action { Buy, Sell } class Order { def security def quantity, limitPrice boolean allOrNone def valueCalculation Action action def buy(Integer quantity, String security) { this.quantity = quantity this.security = security this.action = Action.Buy return this } def sell(Integer quantity, String security) { this.quantity = quantity this.security = security this.action = Action.Sell return this } def limitPrice(Integer limit) { this.limitPrice = limit; return this } def allOrNone(boolean allOrNone) { this.allOrNone = allOrNone; return this } def valueAs(Closure valueCalculation) { this.valueCalculation = valueCalculation; return this } String toString() { "$action $quantity shares of $security at valuation of ${valueCalculation(quantity, limitPrice)}" } } println new Order() .sell(150, "IBM") .limitPrice(300) .allOrNone(true) .valueAs{ qty, unitPrice -> qty * unitPrice - 100 } println new Order() .buy(200, "GOOG") .limitPrice(200) .allOrNone(true) .valueAs{ qty, unitPrice -> qty * unitPrice - 500 } Sell 150 shares of IBM at valuation of 44900 Buy 200 shares of GOOG at valuation of 39500
  149. 149. …Stock Exchange Order DSL… DSLs 2010 - 149 ©ASERT2006-2010 From: customer@finance-broker.org To: Guillaume Subject: Project Request Date: Wednesday morning Dear Guillaume, That version was great but can you make the DSL a little more fluent. The brokers aren’t programmers after all! Thanks, Happy Customer
  150. 150. …Stock Exchange Order DSL… DSLs 2010 - 150 ©ASERT2006-2010 class Order { def security def quantity def limitPrice def allOrNone def value def bs def buy(securityQuantity, closure) { bs = 'Bought' buySell(securityQuantity, closure) } def sell(securityQuantity, closure) { bs = 'Sold' buySell(securityQuantity, closure) } private buySell(securityQuantity, closure) { // multiple assignment (security, quantity) = [securityQuantity.security, securityQuantity.quantity] // better clone the closure to avoid multi-threading access issues def c = closure.clone() // delegate the method calls inside the closure to our methodMissing c.delegationStrategy = Closure.DELEGATE_ONLY c.delegate = this def valuation = c() println "$bs $quantity $security.name at valuation of $valuation" } // methods inside the closure will assign the Order properties def methodMissing(String name, args) { this."$name" = args[0] } ...
  151. 151. …Stock Exchange Order DSL… DSLs 2010 - 151 ©ASERT2006-2010 ... def getTo() { this } def valueAs(closure) { value = closure(quantity, limitPrice) } } class Security { String name } class Quantity { Security security Integer quantity } Integer.metaClass.getShares = { -> delegate } Integer.metaClass.of = { new Quantity(security: it, quantity: delegate) } class CustomBinding extends Binding { def getVariable(String symbol) { // create a new order each time // for when you pass several orders if (symbol == "newOrder") new Order() // otherwise, it's an instrument // trick to avoid using strings: use IBM instead of 'IBM' else new Security(name: symbol) } } // use the script binding for retrieving IBM, etc. binding = new CustomBinding() newOrder.to.buy(100.shares.of(IBM)) { limitPrice 300 allOrNone true valueAs { qty, unitPrice -> qty * unitPrice - 200 } } newOrder.to.sell 200.shares.of(GOOG), { limitPrice 200 allOrNone false valueAs { qty, unitPrice -> qty * unitPrice - 500 } }
  152. 152. …Stock Exchange Order DSL… DSLs 2010 - 152 ©ASERT2006-2010 From: customer@finance-broker.org To: Guillaume Subject: Project Request Date: Wednesday lunch time Dear Guillaume, That version was great but can we simplify the constraint to remove the parameters, i.e.: change { qty, unitPrice -> qty * unitPrice - 200 } to this: { qty * unitPrice - 200 } Thanks, Happy Customer
  153. 153. …Stock Exchange Order DSL… DSLs 2010 - 153 ©ASERT2006-2010 class Order { ... def allOrNone def valueCalculation def bs ... private buySell(securityQuantity, closure) { ... valueCalculation = c() // debug print resulting order println toString() return this } ... def valueAs(Closure wrapee) { // in order to be able to define closures like { qty * unitPrice } without having // to explicitly pass the parameters to the closure we can wrap the closure inside // another one and that closure sets a delegate to the qty and unitPrice variables def wrapped = { qty, unitPrice -> def cloned = wrapee.clone() cloned.resolveStrategy = Closure.DELEGATE_ONLY cloned.delegate = [qty: qty, unitPrice: unitPrice] cloned() } return wrapped } String toString() { "$bs $quantity shares of $security.name and valuation of ${valueCalculation(quantity, limitPrice)}" } } newOrder.to.buy(100.shares.of(IBM)) { limitPrice 300 allOrNone true valueAs { qty * unitPrice - 500 } } newOrder.to.sell 200.shares.of(GOOG), { limitPrice 200 allOrNone false valueAs { qty * unitPrice - 100 } }
  154. 154. …Stock Exchange Order DSL… DSLs 2010 - 154 ©ASERT2006-2010 From: customer@finance-broker.org To: Guillaume Subject: Project Request Date: Wednesday afternoon Dear Guillaume, Fantastic! This is getting better all the time! But can we get rid most of the ‘.’ and bracket symbols! Thanks, Happy Customer
  155. 155. …Stock Exchange Order DSL… DSLs 2010 - 155 ©ASERT2006-2010 // Characteristics of the order: "of GOOG {...}" def of(SecurityAndCharacteristics secAndCharact) { security = secAndCharact.security def c = secAndCharact.characteristics.clone() c.delegationStrategy = Closure.DELEGATE_ONLY c.delegate = this c() // debug print of the resulting order println toString() return this } // Valuation closure: "of { qty, unitPrice -> ... }" def of(Closure valueCalculation) { // in order to be able to define closures like { qty * unitPrice } // without having to explicitly pass the parameters to the closure // we can wrap the closure inside another one // and that closure sets a delegate to the qty and unitPrice variables def wrapped = { qty, unitPrice -> def cloned = valueCalculation.clone() cloned.resolveStrategy = Closure.DELEGATE_ONLY cloned.delegate = [qty: qty, unitPrice: unitPrice] cloned() } return wrapped } String toString() { "$action $quantity shares of $security.name at limit price of $limitPrice" } } // ... http://groovyconsole.appspot.com/script/226001 by glaforge
  156. 156. …Stock Exchange Order DSL… DSLs 2010 - 156 ©ASERT2006-2010 // ... class Security { String name } class SecurityAndCharacteristics { Security security Closure characteristics } class CustomBinding extends Binding { def getVariable(String word) { // return System.out when the script requests to write to 'out' if (word == "out") System.out // don't thrown an exception and return null // when a silent sentence word is used, // like "to" and "the" in our DSL null } } // Script helper method for "GOOG {}", "VMW {}", etc. def methodMissing(String name, args) { new SecurityAndCharacteristics( security: new Security(name: name), characteristics: args[0] ) } // Script helper method to make "order to" silent // by just creating our current order def order(to) { new Order() } // use the script binding for silent sentence words like "to", "the" binding = new CustomBinding() // syntax for 200.shares Integer.metaClass.getShares = { -> delegate }
  157. 157. …Stock Exchange Order DSL… DSLs 2010 - 157 ©ASERT2006-2010 // ---- Stock exchange orders DSL ---- order to buy 200.shares of GOOG { limitPrice 500 allOrNone false at the value of { qty * unitPrice - 100 } } order to sell 150.shares of VMW { limitPrice 80 allOrNone true at the value of { qty * unitPrice } } http://groovyconsole.appspot.com/script/226001 by glaforge
  158. 158. …Stock Exchange Order DSL DSLs 2010 - 158 ©ASERT2006-2010 From: customer@finance-broker.org To: Guillaume Subject: Project Request Date: Wednesday evening Dear Guillaume, Brilliant! Even our CEO could write orders! Thanks, Happy Customer
  159. 159. THURSDAY DSLs 2010 - 159 ©ASERT2006-2010 http://t1.gstatic.com/images?q=tbn:_VBloEP8YC-6IM:http://msp248.photobucket.com/albums/gg171/ingrid2002/TextPL252028
  160. 160. Einstein‟s Riddle DSL … DSLs 2010 - 160 ©ASERT2006-2010 From: customer@acme.org To: Paul King Subject: Project Request Date: Early morning Dear Paul, We would like a DSL for capturing our business rules. Our business rules are captured in the form of logic clauses. They are very much like those found in Einstein’s riddle. Thanks, Happy Customer
  161. 161. Einstein‟s Riddle… • Wikipedia: The zebra puzzle is a well- known logic puzzle – It is often called Einstein's Puzzle or Einstein's Riddle because it is said to have been invented by Albert Einstein as a boy, with the claim that Einstein said “only 2 percent of the world's population can solve it.” – The puzzle is also sometimes attributed to Lewis Carroll. However, there is no known evidence for Einstein's or Carroll's authorship; and the original puzzle cited below mentions brands of cigarette, such as Kools, that did not exist during Carroll's lifetime or Einstein's boyhood DSLs 2010 - 161 ©ASERT2006-2010
  162. 162. …Einstein‟s Riddle DSLs 2010 - 162 ©ASERT2006-2010 • Some premises: – The British person lives in the red house – The Swede keeps dogs as pets – The Dane drinks tea – The green house is on the left of the white house – The green homeowner drinks coffee – The man who smokes Pall Mall keeps birds – The owner of the yellow house smokes Dunhill – The man living in the center house drinks milk – The Norwegian lives in the first house – The man who smokes Blend lives next to the one who keeps cats – The man who keeps the horse lives next to the man who smokes Dunhill – The man who smokes Bluemaster drinks beer – The German smokes Prince – The Norwegian lives next to the blue house – The man who smokes Blend has a neighbor who drinks water • And a question: – Who owns the fish?
  163. 163. Einstein‟s Riddle : Prolog ©ASERT2006-2010 % from http://www.baptiste-wicht.com/2010/09/solve-einsteins-riddle-using-prolog % Preliminary definitions persons(0, []) :- !. persons(N, [(_Men,_Color,_Drink,_Smoke,_Animal)|T]) :- N1 is N-1, persons(N1,T). person(1, [H|_], H) :- !. person(N, [_|T], R) :- N1 is N-1, person(N1, T, R). % The Brit lives in a red house hint1([(brit,red,_, _, _)|_]). hint1([_|T]) :- hint1(T). % The Swede keeps dogs as pets hint2([(swede,_,_,_,dog)|_]). hint2([_|T]) :- hint2(T). % The Dane drinks tea hint3([(dane,_,tea,_,_)|_]). hint3([_|T]) :- hint3(T). % The Green house is on the left of the White house hint4([(_,green,_,_,_),(_,white,_,_,_)|_]). hint4([_|T]) :- hint4(T). % The owner of the Green house drinks coffee. hint5([(_,green,coffee,_,_)|_]). hint5([_|T]) :- hint5(T). ... DSLs 2010 - 163
  164. 164. Einstein‟s Riddle DSL … DSLs 2010 - 164 ©ASERT2006-2010 From: customer@acme.org To: Paul King Subject: Project Request Date: Early morning Dear Paul, Thanks for your Prolog solution but we don’t have Prolog installed. Do you have a version that runs on the JVM? Thanks, Happy Customer
  165. 165. Einstein‟s Riddle : Polyglot ©ASERT2006-2010 @GrabResolver('http://dev.inf.unideb.hu:8090/archiva/repository/internal') //@Grab('jlog:jlogic-debug:1.3.6') @Grab('org.prolog4j:prolog4j-api:0.2.0') // uncomment one of the next three lines //@Grab('org.prolog4j:prolog4j-jlog:0.2.0') @Grab('org.prolog4j:prolog4j-tuprolog:0.2.0') //@Grab('org.prolog4j:prolog4j-jtrolog:0.2.0') import org.prolog4j.* def p = ProverFactory.prover p.addTheory(new File('/GroovyExamples/tuProlog/src/einstein.pl').text) def sol = p.solve("solution(Persons).") //println sol.solution.get('Persons') // jlog to avoid converter println sol.get('Persons') // jtrolog/tuProlog DSLs 2010 - 165
  166. 166. Einstein‟s Riddle DSL … DSLs 2010 - 166 ©ASERT2006-2010 From: customer@acme.org To: Paul King Subject: Project Request Date: Early morning Dear Paul, Thanks for that version but in terms of maintaining the rules, we would like a more fluent expression of the rules rather than Prolog? Any thoughts? Thanks, Happy Customer
  167. 167. Einstein‟s Riddle : Polyglot w/ DSL… ©ASERT2006-2010 // define some domain classes and objects enum Pet { dog, cat, bird, fish, horse } enum Color { green, white, red, blue, yellow } enum Smoke { dunhill, blends, pallmall, prince, bluemaster } enum Drink { water, tea, milk, coffee, beer } enum Nationality { Norwegian, Dane, Brit, German, Swede } dogs = dog; birds = bird; cats = cat; horses = horse a = owner = house = the = abode = person = man = is = to = side = next = who = different = 'ignored' DSLs 2010 - 167 // some preliminary definitions p = ProverFactory.prover hintNum = 1 p.addTheory(''' persons(0, []) :- !. persons(N, [(_Men,_Color,_Drink,_Smoke,_Animal)|T]) :- N1 is N-1, persons(N1,T). person(1, [H|_], H) :- !. person(N, [_|T], R) :- N1 is N-1, person(N1, T, R). ''')
  168. 168. …Einstein‟s Riddle : Polyglot w/ DSL… ©ASERT2006-2010 DSLs 2010 - 168 // define some helper methods (our interface to prolog) def addPairHint(Map m) { def from = m.from?.toString()?.toLowerCase() p.addTheory(""" hint$hintNum([(${from ?: '_'},${m.color ?: '_'},${m.drink ?: '_'},${m.smoke ?: '_'},${m.pet ?: '_'})|_]). hint$hintNum([_|T]) :- hint$hintNum(T). """) hintNum++ } def addPositionHint(Map m, int pos) { def from = m.from?.toString()?.toLowerCase() p.addTheory(""" hint$hintNum(Persons) :- person($pos, Persons, (${from ?: '_'},${m.color ?: '_'},${m.drink ?: '_'},${m.smoke ?: '_'},${m.pet ?: '_'})). """) hintNum++ } def addToLeftHint(Map left, Map right) { p.addTheory(""" hint$hintNum([(_,$left.color,_,_,_),(_,$right.color,_,_,_)|_]). hint$hintNum([_|T]) :- hint$hintNum(T). """) hintNum++ } ...
  169. 169. …Einstein‟s Riddle : Polyglot w/ DSL… ©ASERT2006-2010 DSLs 2010 - 169 // now implement DSL in terms of helper methods def the(Nationality n) { def ctx = [from:n] [ drinks: { d -> addPairHint(ctx + [drink:d]) }, smokes: { s -> addPairHint(ctx + [smoke:s]) }, keeps: { p -> addPairHint(ctx + [pet:p]) }, rears: { p -> addPairHint(ctx + [pet:p]) }, owns:{ _the -> [first:{ house -> addPositionHint(ctx, 1) }] }, has:{ _a -> [pet: { a -> addPairHint(ctx + [pet:a]) }] + Color.values().collectEntries{ c -> [c.toString(), { _dummy -> addPairHint(ctx + [color:c]) } ] } }, lives: { _next -> [to: { _the -> Color.values().collectEntries{ c -> [c.toString(), { _dummy -> addNeighbourHint(ctx, [color:c]) } ] } }]} ] } ...
  170. 170. …Einstein‟s Riddle : Polyglot w/ DSL… ©ASERT2006-2010 DSLs 2010 - 170 // now define the DSL the man from the centre house drinks milk the Norwegian owns the first house the Dane drinks tea the German smokes prince the Swede keeps dogs // alternate ending: has a pet dog the Brit has a red house // alternate ending: red abode the owner of the green house drinks coffee the owner of the yellow house smokes dunhill the person known to smoke pallmall rears birds // alt’n8 end: keeps birds the man known to smoke bluemaster drinks beer the green house is on the left side of the white house the man known to smoke blends lives next to the one who keeps cats the man known to keep horses lives next to the man who smokes dunhill the man known to smoke blends lives next to the one who drinks water the Norwegian lives next to the blue house
  171. 171. Einstein‟s Riddle DSL … DSLs 2010 - 171 ©ASERT2006-2010 From: customer@acme.org To: Paul King Subject: Project Request Date: Early morning Dear Paul, That’s great. We even get some code completion When using an IDE. Is there anything more we can do to get more completion? Thanks, Happy Customer
  172. 172. …Einstein‟s Riddle : Polyglot w/ DSL… ©ASERT2006-2010 DSLs 2010 - 172 // now implement DSL in terms of helper methods def the(Nationality n) { def ctx = [from:n] [ drinks: { d -> addPairHint(ctx + [drink:d]) }, smokes: { s -> addPairHint(ctx + [smoke:s]) }, keeps: { p -> addPairHint(ctx + [pet:p]) }, ... ] } ... the German smokes prince the(German).smokes(prince) n = German ctx = [from: German] [drinks: …, smokes: { s -> addPairHint([from: German, smoke: s]) }, keeps: …, … ] addPairHint([from: German, smoke: prince])
  173. 173. …Einstein‟s Riddle : Polyglot w/ DSL… • Some parts of our DSL are automatically statically inferred, e.g. typing „bl‟ and then asking for completion yields: • But other parts are not known, e.g. the word „house‟ in the fragment below: DSLs 2010 - 173 ©ASERT2006-2010 „house‟ is key for a Map and could be any value
  174. 174. …Einstein‟s Riddle : Polyglot w/ DSL ©ASERT2006-2010 DSLs 2010 - 174 class HousePlaceHolder { def c1, script def house(_is) { [on: { _the -> [left: { _side -> [of: { __the -> Color.values().collectEntries { c2 -> [c2.toString(), { _dummy -> script.addToLeftHint( [color: c1], [color: c2] )}]} }]}]}] } } def the(Color c1) { new HousePlaceHolder(c1:c1, script:this) } def the(Color c1) {[ house: { _is -> [on: { _the -> [left: { _side -> [of: { __the -> Color.values().collectEntries{ c2 -> [c2.toString(), { _dummy -> addToLeftHint([color:c1], [color:c2]) }]} }]}]}]} ]} „house‟ is now understood
  175. 175. Einstein‟s Riddle DSL … DSLs 2010 - 175 ©ASERT2006-2010 From: customer@acme.org To: Paul King Subject: Project Request Date: Early morning Dear Paul, That’s fantastic! But we have just started standardizing on Choco as our logic solving engine. I guess we need to start from scratch. Let me know what you think. Thanks, Happy Customer
  176. 176. Einstein‟s Riddle : Choco w/ DSL… ©ASERT2006-2010 DSLs 2010 - 176 @GrabResolver('http://www.emn.fr/z-info/choco-solver/mvn/repository/') @Grab('choco:choco:2.1.1-SNAPSHOT') import static choco.Choco.* import choco.kernel.model.variables.integer.* def m = new choco.cp.model.CPModel() m.metaClass.plus = { m.addConstraint(it); m } def s = new choco.cp.solver.CPSolver() choco.Choco.metaClass.static.eq = { c, v -> delegate.eq(c, v.ordinal()) } def makeEnumVar(st, arr) { choco.Choco.makeIntVar(st, 0, arr.size()-1, choco.Options.V_ENUM) } pets = new IntegerVariable[num] colors = new IntegerVariable[num] smokes = new IntegerVariable[num] drinks = new IntegerVariable[num] nations = new IntegerVariable[num] (0..<num).each { i -> pets[i] = makeEnumVar("pet$i", pets) colors[i] = makeEnumVar("color$i", colors) smokes[i] = makeEnumVar("smoke$i", smokes) drinks[i] = makeEnumVar("drink$i", drinks) nations[i] = makeEnumVar("nation$i", nations) } ...
  177. 177. …Einstein‟s Riddle : Choco w/ DSL… ©ASERT2006-2010 DSLs 2010 - 177 // define DSL (simplistic non-refactored version) def neighbours(var1, val1, var2, val2) { and( ifOnlyIf(eq(var1[0], val1), eq(var2[1], val2)), implies(eq(var1[1], val1), or(eq(var2[0], val2), eq(var2[2], val2))), implies(eq(var1[2], val1), or(eq(var2[1], val2), eq(var2[3], val2))), implies(eq(var1[3], val1), or(eq(var2[2], val2), eq(var2[4], val2))), ifOnlyIf(eq(var1[4], val1), eq(var2[3], val2)) ) } iff = { e1, c1, e2, c2 -> and(*(0..<num).collect{ ifOnlyIf(eq(e1[it], c1), eq(e2[it], c2)) }) } ... // define the DSL in terms of DSL implementation def the(Nationality n) { def ctx = [nations, n] [ drinks:iff.curry(*ctx, drinks), smokes:iff.curry(*ctx, smokes), keeps:iff.curry(*ctx, pets), rears:iff.curry(*ctx, pets), owns:{ _the -> [first:{ house -> eq(nations[first], n)}] }, ...
  178. 178. …Einstein‟s Riddle : Choco w/ DSL… ©ASERT2006-2010 DSLs 2010 - 178 // define rules m += all pets are different m += all colors are different m += all smokes are different m += all drinks are different m += all nations are different m += the man from the centre house drinks milk m += the Norwegian owns the first house m += the Dane drinks tea m += the German smokes prince m += the Swede keeps dogs // alternate ending: has a pet dog m += the Brit has a red house // alternate ending: red abode m += the owner of the green house drinks coffee m += the owner of the yellow house smokes dunhill m += the person known to smoke pallmall rears birds // alt end: keeps birds m += the man known to smoke bluemaster drinks beer m += the green house is on the left side of the white house m += the man known to smoke blends lives next to the one who keeps cats m += the man known to keep horses lives next to the man who smokes dunhill m += the man known to smoke blends lives next to the one who drinks water m += the Norwegian lives next to the blue house ...
  179. 179. …Einstein‟s Riddle : Choco w/ DSL • Output: DSLs 2010 - 179 ©ASERT2006-2010 def pretty(s, c, arr, i) { c.values().find{ it.ordinal() == s.getVar(arr[i])?.value } } // invoke logic solver s.read(m) def more = s.solve() while (more) { for (i in 0..<num) { print 'The ' + pretty(s, Nationality, nations, i) print ' has a pet ' + pretty(s, Pet, pets, i) print ' smokes ' + pretty(s, Smoke, smokes, i) print ' drinks ' + pretty(s, Drink, drinks, i) println ' and lives in a ' + pretty(s, Color, colors, i) + ' house' } more = s.nextSolution() } Solving Einstein's Riddle: The Norwegian has a pet cat smokes dunhill drinks water and lives in a yellow house The Dane has a pet horse smokes blends drinks tea and lives in a blue house The Brit has a pet bird smokes pallmall drinks milk and lives in a red house The German has a pet fish smokes prince drinks coffee and lives in a green house The Swede has a pet dog smokes bluemaster drinks beer and lives in a white house
  180. 180. FRIDAY DSLs 2010 - 180 ©ASERT2006-2010 http://t3.gstatic.com/images?q=tbn:mgkj1lXpQ2-uWM:http://i298.photobucket.com/albums/mm269/bearyjuicylicious/comments
  181. 181. Important business meetings all afternoon! DSLs 2010 - 181 ©ASERT2006-2010 http://www.flickr.com/photos/bobswanson/5093775403/sizes/l/in/pool-52240148330@N01/
  182. 182. Topics • Introduction • Groovy DSL Features • A Week In The Life Of DSL INC Summary • More Info DSLs 2010 - 182 ©ASERT2006-2010
  183. 183. Some Finishing Guidelines • Language and program evolve together … In the end your program will look as if the language had been designed for it … you end up with code which is clear, small, and efficient. – Paul Graham • Don‟t think just about Coding up your DSL – But also about its target audience, its evolution, required tool support and its testability DSLs 2010 - 183
  184. 184. Start small, with key concepts Beware over-engineering!
  185. 185. Grow your language progressively
  186. 186. Get your hands dirty Play with the end-users
  187. 187. Let your DSL fly, it‟s not yours, it‟s theirs!
  188. 188. Tight feedback loop Iterative process
  189. 189. Stay humble, You can‟t get it right the 1st time. Don‟t design alone at your desk Involve the end users from the start
  190. 190. Playing it safe in a sandbox
  191. 191. Topics • Introduction • Groovy DSL Features • A Week In The Life Of DSL INC • Summary More Info DSLs 2010 - 191 ©ASERT2006-2010
  192. 192. Further Info… DSLs 2010 - 192 ©ASERT2006-2010 • Compilers : Principles, Techniques, and Tools/ Edition 2, Alfred Aho, Ravi Sethi, Jeffrey Ullman, Monica Lam • Practical API Design : Confessions of a Java Framework Architect, Jaroslav Tulach • Language Implementation Patterns : Create Your Own Domain-Specific and General Programming Languages, Terence Parr
  193. 193. …Further Info DSLs 2010 - 193 ©ASERT2006-2010 • A model-driven framework for domain specific languages, Martin Karlsch • Design Guidelines for Domain Specific Languages, Gabor Karsai et al • Program Comprehension for Domain- Specific Languages, Pereira et al • Diagrammatic Representations in Domain- Specific Languages, Konstantinos Tourlas • DSLs in Action, Debasish Ghosh • Domain-Specific Languages, Martin Fowler • DSLs in Boo : Domain Specific Languages in .NET, Ayende Rahien
  194. 194. GinA 2ed “ReGinA” is coming! DSLs 2010 - 194 Contains a chapter on DSLs!
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