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1 point by shader 5137 days ago | link | parent

Sounds like you're looking for some kind of hygienic macros, and may have rediscovered the logic behind scheme adopting them in the first place.

It is possible that properly handling modules at the core language level requires that either macros are only ever expanded and evaluated in their original context, or hygiene must be used to encapsulate that context in the macro-expansion. Or leave it without restrictions, and hope people follow the guidelines.

Not all hygienic macro systems are cumbersome or complicated, and it's possible that we could create one that permits selective breaking of hygiene as desired. One candidate would be an implementation of SRFI 72: http://srfi.schemers.org/srfi-72/srfi-72.html

Hygiene has been discussed on this forum, and I think a few systems may exist already.



1 point by Pauan 5137 days ago | link

Wouldn't name-munging solve it also? Suppose, for instance, that you have two modules:

  ; foo.arc
  
  (= message* "hello")
  (mac ret () message*)
  
  
  ; bar.arc
  
  (import (ret) "foo.arc")
  (ret) -> error: message* is undefined
Okay, but what if every symbol was transparently prefixed with the module's name, or a gensym or something? Something like this:

  ; foo.arc
  
  (= foo@message* "hello")
  (main@mac foo@ret () foo@message*)
  
  
  ; bar.arc
  
  (main@import (bar@ret) "foo.arc")
  (bar@ret) -> "hello"
This is all handled by the interpreter, so normal users don't see it. Anyways, now `ret` would expand to this:

  (foo@message*)
Which would refer to the correct binding in the correct namespace. Hm... but then what if the macro actually does want to grab a value defined in bar.arc? Tricky.

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1 point by rocketnia 5137 days ago | link

I think your question is really "Wouldn't name-munging accomplish hygiene?" :)

What you're talking about is pretty similar to how Racket accomplishes hygiene by way of 'read-syntax. Everything's wrapped up so you know what its source file is, and that's all I know for now. :-p Seems Racket's system is pretty cumbersome, but then that's probably because it's very static, with modules revealing what they export before any of the exported values are actually calculated.

What you're talking about also sounds extremely similar to Common Lisp's approach to namespaces. I don't know that approach very well, but it could act as some sort of example. ^^

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