• VladD2 <vc rsdn.ru> Dec 17 2010

VladD2 <vc rsdn.ru> writes:

Don Wrote:

 You missed: pattern matching, 


 Yes, you've got me there. I've assumed that pattern matching, while a 
 major feature, is not fundamental to the Nemerle macro-system, but I may 
 be mistaken.
 
 One obvious difference which *is* fundamental is that Nemerle macros 
 allow new syntax.
 
 Am I correct in thinking that Nemerle always requires complete ASTs?
 That is, given a name "x", can you access variables "x1", "x2", "x3" ?
 
  > quasi-quotation,
 
 No, that's present in D. It's the primary reason I say that the 
 differences are mostly syntactic, since I see this as THE fundamental 
 feature. You need to be able to reenter the macro system after you have 
 left it. Once you can do that, you can do pretty much anything.


You not understand... pattern matching and quasi-quotation tightly bound. The
quasi-quotation produce instances of Algebraic Data Type (AlgTD) which can be
decomposed (and matched) by pattern matching (PM). We use PM to "read" code of
a project.

For example, see C# grammar:
http://code.google.com/p/nemerle/source/browse/nemerle/trunk/snippets/csharp-parser/CSharpParser/Parser.n?r=9436
which made by PegGrammar macro:
http://code.google.com/p/nemerle/source/browse/nemerle/trunk/snippets/peg-parser/Nemerle.Peg.Macros?r=9436

Or see our foreach macro:
http://code.google.com/p/nemerle/source/browse/nemerle/trunk/macros/core.n?r=9436#508

 running of fully functional Nemerle
 code in compile time, 


 Yes, but that's a different issue. In D, running code at compile time is 
   regarded as an aspect of constant-folding, and is not restricted to 
 macros.


The constant-folding is too limited solution. 

The power of of macros, including the ability to use are any libraries and any
data sources.

And ... you use enterpretation... slow way.

 access to compiler API in macros


 In practice, has to be a library, right? Otherwise the compiler 
 internals would be exposed? (This is an issue we're struggling with).


Yes. The Nemerle compiler is library. :)
Unfortunately Nemerle API is not pretty clear. But I believe it's a right way.

P.S.

Sorry for my (Russian) English. :)