Building

    DSL         s
on the CLR and DLR
VitalyBaum
                          vbaum@live.com
                          butaji




MaximMoiseev
maxim.moiseev@gmail....
http://altdotnet.org




http://spbalt.net/
The short annotation

DOMAIN SPECIFIC LANGUAGES
Domain Specific Languages (DSLs)
are limited forms of computer language
designed for a specific class of problems.
Martin Fowler
    “(DSL) is a computer language that's
targeted to a particular kind of problem,
 rather than a general pu...
Paul Graham
“*Lisp Programmers+ follow a principle
which could be called bottom-up design--
changing the language to suit ...
DSLS CLASSIFICATION
Types of DSL

         Internal                   External
• Written in host           • Separate to host
  language      ...
Types of DSL

         Internal                    External
• Tied to base language   •   Lack of Symbolic
• Awkward with ...
Types of DSL

           Internal                  External
•   LINQ (C#)              •   Regexp
•   Monads (Haskell)    ...
Types of DSL
Graphical DSL
              Log
Workflow    Activity


             Clear
            Activity


           S...
DSL Oriented .NET Languages

LANGUAGES
F#       Ruby
     Lisp
                 Python

 Boo

C#
                 Smalltalk
F#       Ruby
     Lisp
                 Python
CLR
 Boo                DLR
C#
                 Smalltalk
I <3
The important advantages over a GPL

WHY SHOULD WE USE DSL?
Why should we use DSL
• Domain-specific abstractions: a DSL provides pre-
  defined abstractions to directly represent
  c...
Why should we use DSL

• Domain-specific error checking: a DSL enables
  building static analyzers that can find more
  er...
Why should we use DSL

• Domain-specific tool support: a DSL creates
  opportunities to improve any tooling aspect of
  a ...
Why is DSL good?

              Business
             Peoples and
               “Rules”



Developers
 and their
 “Magic”
Read                          and          Write
            director of finance for the client bank to edit, test,
and de...
Read   Write
DSL Building Patterns

PATTERNS
Better code readability

•   Fluent interfaces
•   Extension methods
•   LINQ
•   Workflows
•   Syntactic sugar
•   AdHoc ...
Fluent interfaces
Expect
  .Once
  .On(…)
  .Method(…)
  .WithAnyArguments()
  .Will(
       Return.Value(…)
  )

        ...
Fluent interfaces
Expect                   public static Expect {…}
  .Once                    IRecieverSyntax
  .On(…)   ...
Fluent interfaces
public class ExpectationBuilder:
  IReceiverSyntax,
  IMethodSyntax,
  IArgumentSyntax,
  IActionSyntax ...
Combinations



today.at 3.pm
3.days.from_today at(3.pm)
Timespan Literals

print(50s) // 50 seconds
print(1d) // 1 day
print(2m) // 2 minutes
print(42ms) // 42 miliseconds
print(...
String interpolation



print("Now is ${date.Now}.")
print("Tomorrow will be ${date.Now +
  1d}")
Extension methods

DateTime now =
                       VS   DateTime res =
   DateTime.Now;              3.Days()
TimeSp...
Extension methods
public static class MyExtensions {

    public static TimeSpan Days(this int i) {
         return TimeSp...
Man, there’s LINQ already
      Can’t we use that?
We do
LINQ
string s1 = GetS1();            VS var res =
string s2 = GetS2();                    from a in GetS1()
string res =  ...
LINQ
public class Maybe<T> {

      public T Value { get; private set; }
      public bool HasValue { get; private set; }
...
LINQ
public static Maybe<T> ToMaybe<T>(this T value) {
  return new Maybe<T>(value);
}

public static Maybe<U> SelectMany<...
Important

• LINQ is a Monad
• F# Workflows are monads
• What isn’t?!

 "[W]hen the designers of F# talked with the design...
C# is no fun.
Want more!
Yeah?! F# you!
Workflows
type Чо<'a> =
  | Ничо
  | Чото of 'a

let bindMaybe x f =
   match x with
   | Ничо -> Ничо
   | Чото y -> f y
...
Workflows
let first =
   чокак ,
      let! x = Чото 6
      let! y = Чото 5
      return (x + y)
   }

let second =
   чо...
Syntactic sugar
Sweeties

•   Partial application
•   Pipelining
•   Composition
•   List comprehension
•   Operators overriding
•   AST m...
Million years ago there wasn’t LINQ
 And I still program C# 2. Can I have some DSL?
AdHoc LINQ
Calculation<Item> calculation =
         Time.Between(
            Select.First(thisYear),
            Select.L...
Simples DSLs on .NET

SAMPLES
Validation DSL : IronPython




discussion    demo       discussion
Validation DSL : IronPython

public class User : ValidationBase
{
   [Validation("first_name_length")]
   public string Fi...
Validation DSL : IronPython

<rule name="last_name_length"
 message="Last name must be at least 2
 characters">
  <![CDATA...
Validation DSL : IronPython




PythonEngine::Execute(“python code here”)
Validation DSL : Boo


             Rules
             (Boo)


     Model
      (C#)
                 ASP.NET
            ...
Validation DSL : Boo

public class User
{
  public string Username { get; set; }
  public string Password { get; set; }
}
Validation DSL : Boo

rule_for "User":
  validate def(x):
      results = create_results()
      if string.IsNullOrEmpty(x...
Validation DSL : Boo

Boo.Lang.Interpreter. InteractiveInterpreter
  _interpreter;
Func<List<ValidationResult>> createResu...
Validation DSL : Boo
Boo:
results.Add(fail("Username and Password are required"))
C#:
CompilerContext ctx =
  _interpreter...
Object2RSS DSL : Boo


             Rules
             (Boo)


     Model
      (C#)
                 ASP.NET
            ...
Object2RSS DSL : Boo
public class Product
   {
          public int Id { get; set; }

          public string Name { get; ...
Object2RSS DSL : Boo
rule_for "Product":
   title def(x):
        return "${x.Manufacturer.Name.ToUpper()} -
   ${x.Name}"...
Object2RSS DSL : Boo
var engine = new RssDslEngine();
foreach (T item in items)
  {
      writer.WriteStartElement("item")...
Object2RSS DSL : Boo
public string Execute(object o, string field)
     {
              string ruleName = o.GetType().Name...
A BDD framework for .NET and Mono

SPECTER FRAMEWORK
MiniBar specification tutorial
MiniBar specification tutorial
import Specter.Framework
import Bender
context "At Bender's bar":
   _bar as duck
   setup:...
MiniBar specification tutorial
import Specter.Framework
import Bender
context "At Bender's bar":
   _bar as duck
   setup:...
MiniBar specification tutorial
import Specter.Framework                       [NUnit.Framework.SetUp]
import Bender       ...
MiniBar specification tutorial
import Specter.Framework
import Bender
context "At Bender's bar":
   _bar as duck
   setup:...
MiniBar specification tutorial
                  [NUnit.Framework.Test]
import Specter.Framework
import Bender         def...
MiniBar specification tutorial
       [NUnit.Framework.Test]
import Specter.Framework
import Bender
contextdef IfiDrinkMor...
MiniBar specification tutorial
MiniBar specification tutorial

namespace Bender
  class MiniBar:
      def DrinkOneBeer():
            pass
      [getter...
MiniBar specification tutorial
MiniBar specification tutorial
namespace Bender
  class MiniBar:
      def DrinkOneBeer():
            _balance--
        ...
MiniBar specification tutorial
thx.
Need more?
• http://www.microsoft.com/soa/products/oslo.aspx
• http://www.jetbrains.com/mps/index.html
• http://blogs.msdn...
Resources

• http://www.code-
  magazine.com/article.aspx?quickid=0902041
  &page=1 (Building Domain Specific
  Languages ...
Resources

• http://www.paulgraham.com/
• http://martinfowler.com/
• http://en.wikipedia.org/wiki/Domain-
  specific_progr...
Building DSLs On CLR and DLR (Microsoft.NET)
Building DSLs On CLR and DLR (Microsoft.NET)
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Building DSLs On CLR and DLR (Microsoft.NET)

  1. 1. Building DSL s on the CLR and DLR
  2. 2. VitalyBaum vbaum@live.com butaji MaximMoiseev maxim.moiseev@gmail.com moiseev
  3. 3. http://altdotnet.org http://spbalt.net/
  4. 4. The short annotation DOMAIN SPECIFIC LANGUAGES
  5. 5. Domain Specific Languages (DSLs) are limited forms of computer language designed for a specific class of problems.
  6. 6. Martin Fowler “(DSL) is a computer language that's targeted to a particular kind of problem, rather than a general purpose language that's aimed at any kind of software problem.”
  7. 7. Paul Graham “*Lisp Programmers+ follow a principle which could be called bottom-up design-- changing the language to suit the problem.”
  8. 8. DSLS CLASSIFICATION
  9. 9. Types of DSL Internal External • Written in host • Separate to host language language • Conventional use of • Needs the subset of host language compiler/interpreter to syntax execute
  10. 10. Types of DSL Internal External • Tied to base language • Lack of Symbolic • Awkward with Integration mainstream • Complex parser/generator technologies • Ignorant IDEs • (language cacophony)
  11. 11. Types of DSL Internal External • LINQ (C#) • Regexp • Monads (Haskell) • SQL • Workflows (F#) • CSS • Sequence expressions • Ant (F#) • XSLT • List comprehensions (Haskell, Python)
  12. 12. Types of DSL Graphical DSL Log Workflow Activity Clear Activity Shutdown Activity
  13. 13. DSL Oriented .NET Languages LANGUAGES
  14. 14. F# Ruby Lisp Python Boo C# Smalltalk
  15. 15. F# Ruby Lisp Python CLR Boo DLR C# Smalltalk
  16. 16. I <3
  17. 17. The important advantages over a GPL WHY SHOULD WE USE DSL?
  18. 18. Why should we use DSL • Domain-specific abstractions: a DSL provides pre- defined abstractions to directly represent concepts from the application domain. Consequently, domain experts themselves can understand, validate, modify, and often even develop DSL program • Domain-specific concrete syntax: a DSL offers a natural notation for a given domain and avoids syntactic clutter that often results when using a GPL.
  19. 19. Why should we use DSL • Domain-specific error checking: a DSL enables building static analyzers that can find more errors than similar analyzers for a GPL and that can report the errors in language familiar to the domain expert. • Domain-specific optimizations: a DSL creates opportunities for generating optimized code base on domain-specific knowledge, which is usually not available to a compiler for a GPL.
  20. 20. Why should we use DSL • Domain-specific tool support: a DSL creates opportunities to improve any tooling aspect of a development environment, including, editors, debuggers, version control, etc.; the domain-specific knowledge that is explicitly captured by a DSL can be used to provide more intelligent tool support for developers.
  21. 21. Why is DSL good? Business Peoples and “Rules” Developers and their “Magic”
  22. 22. Read and Write director of finance for the client bank to edit, test, and deploy the business rules of the system without any assistance from IT
  23. 23. Read Write
  24. 24. DSL Building Patterns PATTERNS
  25. 25. Better code readability • Fluent interfaces • Extension methods • LINQ • Workflows • Syntactic sugar • AdHoc LINQ
  26. 26. Fluent interfaces Expect .Once .On(…) .Method(…) .WithAnyArguments() .Will( Return.Value(…) ) NMock mocking library usage
  27. 27. Fluent interfaces Expect public static Expect {…} .Once IRecieverSyntax .On(…) IMethodSyntax .Method(…) IArgumentSyntax .WithAnyArguments() IActionSyntax .Will( Return.Value(…) IAction )
  28. 28. Fluent interfaces public class ExpectationBuilder: IReceiverSyntax, IMethodSyntax, IArgumentSyntax, IActionSyntax {…} public IMethodSyntax On(…){ // … return this; } public IArgumentSyntax Method(…){ // … return this; }
  29. 29. Combinations today.at 3.pm 3.days.from_today at(3.pm)
  30. 30. Timespan Literals print(50s) // 50 seconds print(1d) // 1 day print(2m) // 2 minutes print(42ms) // 42 miliseconds print("Tomorrow this time will be: ${date.Now + 1d}")
  31. 31. String interpolation print("Now is ${date.Now}.") print("Tomorrow will be ${date.Now + 1d}")
  32. 32. Extension methods DateTime now = VS DateTime res = DateTime.Now; 3.Days() TimeSpan span = .From( TimeSpan.FromDays(3); DateTime.Now DateTime res = ) now + span;
  33. 33. Extension methods public static class MyExtensions { public static TimeSpan Days(this int i) { return TimeSpan.FromDays(i); } public static DateTime From( this TimeSpan span, DateTime dt) { return dt + span; } }
  34. 34. Man, there’s LINQ already Can’t we use that?
  35. 35. We do
  36. 36. LINQ string s1 = GetS1(); VS var res = string s2 = GetS2(); from a in GetS1() string res = from b in GetS2() string.Empty; select a + b; if(s1 != null && s2 != null){ res = s1 + s2; }
  37. 37. LINQ public class Maybe<T> { public T Value { get; private set; } public bool HasValue { get; private set; } private Maybe() { HasValue = false; } public Maybe(T value) { Value = value; HasValue = true; } public static readonly Maybe<T> Nothing = new Maybe<T>(); }
  38. 38. LINQ public static Maybe<T> ToMaybe<T>(this T value) { return new Maybe<T>(value); } public static Maybe<U> SelectMany<T, U>( this Maybe<T> src, Func<T, Maybe<U>> f) { if (!src.HasValue) { return Maybe<U>.Nothing; } return f(src.Value); }
  39. 39. Important • LINQ is a Monad • F# Workflows are monads • What isn’t?! "[W]hen the designers of F# talked with the designers of Haskell about this, they agreed that the word monad is a bit obscure and sounds a little daunting and that using other names might be wise.“ [F# Workflows and Haskell Monads, Expert F#, p232]
  40. 40. C# is no fun. Want more!
  41. 41. Yeah?! F# you!
  42. 42. Workflows type Чо<'a> = | Ничо | Чото of 'a let bindMaybe x f = match x with | Ничо -> Ничо | Чото y -> f y type MaybeBuilder() = member x.Return(what) = Чото what member x.Bind(m, f) = bindMaybe m f let чокак = new MaybeBuilder()
  43. 43. Workflows let first = чокак , let! x = Чото 6 let! y = Чото 5 return (x + y) } let second = чокак , let! x = Ничо let! y = Чото 5 return x+y }
  44. 44. Syntactic sugar
  45. 45. Sweeties • Partial application • Pipelining • Composition • List comprehension • Operators overriding • AST modifications • Measurement units
  46. 46. Million years ago there wasn’t LINQ And I still program C# 2. Can I have some DSL?
  47. 47. AdHoc LINQ Calculation<Item> calculation = Time.Between( Select.First(thisYear), Select.Last(thisYear) );
  48. 48. Simples DSLs on .NET SAMPLES
  49. 49. Validation DSL : IronPython discussion demo discussion
  50. 50. Validation DSL : IronPython public class User : ValidationBase { [Validation("first_name_length")] public string FirstName { get; set; } }
  51. 51. Validation DSL : IronPython <rule name="last_name_length" message="Last name must be at least 2 characters"> <![CDATA[result = property_value != None and len(property_value) >= 2]]> </rule>
  52. 52. Validation DSL : IronPython PythonEngine::Execute(“python code here”)
  53. 53. Validation DSL : Boo Rules (Boo) Model (C#) ASP.NET MVC Application
  54. 54. Validation DSL : Boo public class User { public string Username { get; set; } public string Password { get; set; } }
  55. 55. Validation DSL : Boo rule_for "User": validate def(x): results = create_results() if string.IsNullOrEmpty(x.Username) return results
  56. 56. Validation DSL : Boo Boo.Lang.Interpreter. InteractiveInterpreter _interpreter; Func<List<ValidationResult>> createResults = (() => new List<ValidationResult>()); _interpreter.SetValue("create_results", createResults);
  57. 57. Validation DSL : Boo Boo: results.Add(fail("Username and Password are required")) C#: CompilerContext ctx = _interpreter.EvalCompilerInput(new FileInput(_filePath)); foreach (CompilerError error in ctx.Errors) { sb.AppendLine(error.Message); }
  58. 58. Object2RSS DSL : Boo Rules (Boo) Model (C#) ASP.NET MVC Application
  59. 59. Object2RSS DSL : Boo public class Product { public int Id { get; set; } public string Name { get; set; } public string Description { get; set; } public double Price { get; set; } public DateTime CreateDate { get; set; } public Manufacturer Manufacturer { get; set; } }
  60. 60. Object2RSS DSL : Boo rule_for "Product": title def(x): return "${x.Manufacturer.Name.ToUpper()} - ${x.Name}" description def(x): return x.Description link def(x): return "http://codevoyeur.com/products/${x.Id}" pubDate def(x): return x.CreateDate.ToString("s")
  61. 61. Object2RSS DSL : Boo var engine = new RssDslEngine(); foreach (T item in items) { writer.WriteStartElement("item"); List<string> fields = RssFieldFactory.Create(); fields.ForEach(x => writer.WriteElementString(x, engine.Execute(item, x))); writer.WriteEndElement(); }
  62. 62. Object2RSS DSL : Boo public string Execute(object o, string field) { string ruleName = o.GetType().Name; if (_rules.ContainsKey(ruleName)) { return _rules[ruleName][field].Invoke(o); } else { throw new ApplicationException("Invalid rule name"); } }
  63. 63. A BDD framework for .NET and Mono SPECTER FRAMEWORK
  64. 64. MiniBar specification tutorial
  65. 65. MiniBar specification tutorial import Specter.Framework import Bender context "At Bender's bar": _bar as duck setup: subject _bar = Bender.MiniBar() specify { _bar.DrinkOneBeer() }.Must.Not.Throw() specify "If I drink 5 beers then I owe 5 bucks": for i in range(5): _bar.DrinkOneBeer() _bar.Balance.Must.Equal(-5) specify "If I drink more than ten beers then I get drunk": for i in range(10): _bar.DrinkOneBeer() { _bar.DrinkOneBeer() }.Must.Throw()
  66. 66. MiniBar specification tutorial import Specter.Framework import Bender context "At Bender's bar": _bar as duck setup: [NUnit.Framework.TestFixture] subject _bar = Bender.MiniBar()class EmptyStack: specify { _bar.DrinkOneBeer() }.Must.Not.Throw() specify "If I drink 5 beers then I owe 5 bucks": for i in range(5): _bar.DrinkOneBeer() _bar.Balance.Must.Equal(-5) specify "If I drink more than ten beers then I get drunk": for i in range(10): _bar.DrinkOneBeer() { _bar.DrinkOneBeer() }.Must.Throw()
  67. 67. MiniBar specification tutorial import Specter.Framework [NUnit.Framework.SetUp] import Bender def SetUp(): context "At Bender's bar": _bar as duck subject _bar = setup: subject _bar = Bender.MiniBar() Bender.MiniBar() specify { _bar.DrinkOneBeer() }.Must.Not.Throw() specify "If I drink 5 beers then I owe 5 bucks": for i in range(5): _bar.DrinkOneBeer() _bar.Balance.Must.Equal(-5) specify "If I drink more than ten beers then I get drunk": for i in range(10): _bar.DrinkOneBeer() { _bar.DrinkOneBeer() }.Must.Throw()
  68. 68. MiniBar specification tutorial import Specter.Framework import Bender context "At Bender's bar": _bar as duck setup: subject _bar = Bender.MiniBar() specify { _bar.DrinkOneBeer() }.Must.Not.Throw() specify "If I drink 5 beers then I owe 5 bucks": for i in range(5): _bar.DrinkOneBeer() _bar.Balance.Must.Equal(-5) [NUnit.Framework.Test] then I get drunk": specify "If I drink more than ten beers for i in range(10): def BarDrinkOneBeerMustNotThrow(): _bar.DrinkOneBeer() Assert.DoesNotThrow(_bar. DrinkOneBeer()) { _bar.DrinkOneBeer() }.Must.Throw()
  69. 69. MiniBar specification tutorial [NUnit.Framework.Test] import Specter.Framework import Bender def IfIDrink5BeersThenIOwe5Bucks(): context "At Bender's bar": for i in range(5): _bar as duck _bar.DrinkOneBeer() setup: Int32MustModule.Must(_bar.Balance, “Bar subject _bar = Bender.MiniBar() -5").Equal(-5) balance must equal specify { _bar.DrinkOneBeer() }.Must.Not.Throw() specify "If I drink 5 beers then I owe 5 bucks": for i in range(5): _bar.DrinkOneBeer() _bar.Balance.Must.Equal(-5) specify "If I drink more than ten beers then I get drunk": for i in range(10): _bar.DrinkOneBeer() { _bar.DrinkOneBeer() }.Must.Throw()
  70. 70. MiniBar specification tutorial [NUnit.Framework.Test] import Specter.Framework import Bender contextdef IfiDrinkMoreThanTenBeersThenIGetDrunk(): "At Bender's bar": _bar as duck setup: for i in range(10): _bar.DrinkOneBeer() subject _bar = Bender.MiniBar() specify { _bar.DrinkOneBeer() }.Must.Not.Throw() Assert.Throws((typeof(InvalidOperationExc specify "If I drink 5 beers then I owe 5 bucks": eption), _bar.DrinkOneBeer()) for i in range(5): _bar.DrinkOneBeer() _bar.Balance.Must.Equal(-5) specify "If I drink more than ten beers then I get drunk": for i in range(10): _bar.DrinkOneBeer() { _bar.DrinkOneBeer() }.Must.Throw()
  71. 71. MiniBar specification tutorial
  72. 72. MiniBar specification tutorial namespace Bender class MiniBar: def DrinkOneBeer(): pass [getter(“Balance”)+ _balance = 0
  73. 73. MiniBar specification tutorial
  74. 74. MiniBar specification tutorial namespace Bender class MiniBar: def DrinkOneBeer(): _balance-- if _balance < -10: raise System.Exception("i'm drunk") [getter(“Balance”)+ _balance = 0
  75. 75. MiniBar specification tutorial
  76. 76. thx.
  77. 77. Need more? • http://www.microsoft.com/soa/products/oslo.aspx • http://www.jetbrains.com/mps/index.html • http://blogs.msdn.com/wesdyer/archive/2008/01/11/the- marvels-of-monads.aspx • http://www.google.com/
  78. 78. Resources • http://www.code- magazine.com/article.aspx?quickid=0902041 &page=1 (Building Domain Specific Languages in C#) • http://bradfordcross.blogspot.com/2009/01/e xternal-dsl-vs-internal-dsl-smack- down_24.html (External DSL vs. Internal DSL Smack Down)
  79. 79. Resources • http://www.paulgraham.com/ • http://martinfowler.com/ • http://en.wikipedia.org/wiki/Domain- specific_programming_language • http://msdn.microsoft.com/en- us/library/bb126235.aspx

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