Tag Archives: Domain Specific Languages

I call B.S. on the Oslo “M” Language

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There was alot of hype around the new Oslo “M” language during the PDC.
It was pretty much explained as a new way to let people create their own domain specific languages.

Since I have a bit of fetish for parsing and DSL’s I attended to the “M Grammar” presentation.

They began by explaining that “M” is so easy that everyone and his mother will now be able to create their own DSL.
And ofcourse they had to show some trivial example that actually wasn’t a DSL at all, but merely a data transformer that transformed a textual list of “contacts” into a structured list.

Maybe I’m just stupid, but when I hear “new” and “easy” I don’t really associate that with old-school LEX and YACC BNF grammars.
But MS apparently do.

Just check this out, this is a small snippet of M Grammar definition of the language itself:

  syntax CompilationUnit
       = decls:ModuleDeclaration*
         =>
           id("Microsoft.M.CompilationUnit")
           {
               Modules { decls }
           };
  
  
   syntax ExportDirective
       = "export" members:ParsedIdentifiers ";"
         =>
         id("Microsoft.M.ExportDirective")
         {
             Names { members }
         };  
  
   syntax ImportAlias
       = "as" alias:ParsedIdentifier
         => alias;
   
   syntax ImportDirective
       = "import" imports:ImportModules ";"
         =>
         id("Microsoft.M.ModuleImportDirective")
         {
             Modules { imports }
         }
                 | "import" targetModule:MemberAccessExpression "{" members:ImportMembers "}" ";"
           =>
           id("Microsoft.M.MemberImportDirective")
           {
               ModuleName { targetModule },
               Members { members }
           };
   
   syntax ImportMember
       = member:ParsedIdentifier alias:ImportAlias?
           => id("Microsoft.M.ImportedName")
           {
               Name { member },
               Alias { alias }
           };

The grammars in “M” was essentially a hybrid of old BNF definitions mixed up with functional programming elements.

I’m not saying that their approach was bad, just that it wasn’t really as easy as they wanted it to be.
There are a few gems in it, but it does in no way lower the compexity of defining a grammar in such a way that everyone will be able to create real DSL’s.

Maybe some people will create a few data transformers using this approach, but I don’t expect to see more “real” DSL’s popping up now than we have seen before..

//Roger

Caramel – Alpha source code is public

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I have added the Caramel code generator to my public repository at google code.
http://code.google.com/p/alsing/

Please note that this is very very alpha and not actually useful yet.

Before it can be used I need to finish the template support and fully implement the DB meta data importer.

But if you are interested in this kind of stuff and want to help out building it, please let me know.

DSLisp

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MyLisp is now named DSLisp – Domain Specific (Language) Lisp.

I have published it as a project on CodePlex:
http://www.codeplex.com/DSLisp

The new name imples the purpose of the project.
To act as a host for DSL’s.

The idea is to compile your DSL into the DSLisp AST.
And then run your DSL inside the DSLisp engine.
By doing this you can very easily add single step debugging and breakpoint support to your DSL. 

See the codeplex site for more info.

Lisp Debugger

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I’m still working on my Lisp language clone.
Today I started to add debugging support to it.
I made the AST aware of the original source code, so each node can reference back to the place it was parsed from, and I also added a bit of call stack features.

I’m pretty satisfied with it so far, it almost feels like a real language now ;-)

Anyway, here is a screenshot of the not so well designed GUI.

 Debugger
Click for full size.

Downloads are available at: 

Source: http://www.puzzleframework.com/roger/mylisp.zip
Binaries: http://www.puzzleframework.com/roger/mylispbin.zip

(The code is written in C#3, VS.NET 2008 solution)

Lisp weekend

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I’ve been reading up a bit on functional programming the last few week, the reason is just to comprehend the new features and possibilities in .NET 3.5 as much as possible.

Anyway, I got a bit carried away and started to read about Lisp, and decided to learn what it’s all about.
So what better way to learn a language than to make your own parser for it is there? ;-)

I started to hammer away on a simple parser, and once the parser was done, I couldn’t stop, so I began writing an engine too.
So after a few hours of Aha moments, I finally got my very own Lisp(ish) code executor and a bit more understanding for the language. ;-)

Well, enough blabbering, here are a few samples of whats currently possible in my still un-named language.

Hello world:

(print 'Hello world!')

Simple function and call:

(defun Mul (x y) 
 (* x y))       

(print (Mul 2 3))

Variables:

(let my-var 'hello lisp') 
(let my-int 123) 
(let my-double 123.456) 
(let half-pi (/ pi 2)) 
(let my-arr (arr 1 2 3 4 5 6 7))

Loops:

(foreach item my-arr 
 (print item))      

(for i 1 20 
 (print i))      

(let i 0) 
(while (< i 20) 
 ((print i) (++ i)))

Lambdas:

(let my-lambda (lambda (x y) (* x y))) 
(my-lambda 2 3)

Delegates:

(let my-delegate Mul) // delegate to Mul 
(let print other-print-func) //redirect the print function to "other-print-func"

Objects:

(let form (new Form)) 
(set form Text 'hello windows forms') 
(let button (new Button)) 
(set button Text 'my button') 
(set-event button Click MyButtonClick) 
(list-add (get form Controls) button) 
(call form Show)

List comprehensions:

(foreach item (select (lambda (concat 'transformed: ' item '!')) 
              (where (lambda (> (get item Length) 3)) 
              (list 'foo' 'bar' 'roger' '.net' 'lisp')))       

      (print item))

The next step will be to make it possible to define your own classes.
Im thinking of emitting true .NET classes and let the methods redirect the calls to the engine.
Thus making it possible to redefine the behaviour of a method in runtime.

That, and find some reason to use it :-P