DSLs Internas
e Ruby
@fabiokung

DSL?
http://www.flickr.com/photos/pragdave/173640462/

DSLs internas
hoje().mais(meses(2));

DSLs internas
hoje().mais(uns(2).meses());

Date.today + 2.months
4.weeks.ago
DSLs internas

var d1 = Hoje mais 2 meses
var d2 = Amanhã menos 1 mês e mais 10 anos e mais 1 dia
Scala: http://gist.github.com/207718 (by Sergio Lopes)
Date.today + 2.months
4.weeks.ago
DSLs internas

DSLs externas

Feature: Search courses
In order to ensure better utilization of courses
Potential students should be able to search for courses
Scenario: Search by topic
Given there are 240 courses without topic "biology"
And there are 2 courses A001, B205 with topic "biology"
When I search for "biology"
Then I should see the following courses:
| Course code |
| A001 |
| B205 |
DSLs externas

o problema...

http://www.flickr.com/photos/stephenvandyke/96983232/

http://www.flickr.com/photos/hand-nor-glove/438290969/
2.maneiras

http://www.flickr.com/photos/aussiegall/759309122/
Top-Down

http://www.flickr.com/photos/akiraikari/2657579326/
Bottom-Up

hora de codar

(define cdar-sequence?
(automaton init
[init : (c -> more)]
[more : (a -> more)
(d -> more)
(r -> end)]
[end : accept]))

hora de codar

http://martinfowler.com/dslwip/SemanticModel.html
Semantic Model

http://martinfowler.com/dslwip/SemanticModel.html
My advice is
to always use a
Semantic
Semantic Model

Resumo
• Module.included(klass)
• obj.extend(Module)
• Class.class_eval { ... }
• obj.send(method)
• obj.instance_eval { ... }

E mais...
• method_missing(name, *args)
• Class.inherited(subclass)
• lambdas, Proc
• ...

Dúvidas?
Obrigado!
fabio.kung @ [gmail locaweb]
http://twitter.com/fabiokung