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Most CLers hate scheme macros since they almost uniformly believe that syntax-rules is the only macro facility. I myself have implemented defmacro using syntax-

by bjoli 8y ago

Most CLers hate scheme macros since they almost uniformly believe that syntax-rules is the only macro facility. I myself have implemented defmacro using syntax-case because it is sometimes nice to have. Hygiene solves the issue of namespacing macros, but at the cost of a very complex implementation. Implementing hygiene is HARD and I don't think it can even be called a solved problem. The current systems have issues that have proven to be hard to resolve.

gpderetta 8y ago
That's intersting, because the lisp 'the right thing' approach [1] calls for correctness and ease of use over simplicity of implementation. [1] as opposed to the alledged 'worse is better' of the unix world.
- bjoli 8y ago
  It is a matter of preference. Sometimes you end up using gensym in scheme as well, especially for introducing identifiers in bulk.
lispm 8y ago
> uniformly believe that syntax-rules is the only macro facility far from it. CLers know that Scheme has zillions of different macro systems. Which makes the whole topic highly confusing and intellectually interesting.
- bjoli 8y ago
  What I meant by that is that CLers usually complain about hygiene as if it was impossible to break. I don't know how many times I have had to explain that syntax-rules is the high level macro facility and that all schemes provide their own lower level macro facility, be it explicit/implicit renaming (chicken), syntax-case (r6rs) or syntactic closures (Chibi?). I understand the complaint that this isn't portable. It isn't. R6RS tried to standardise it. Hopefully r7rs does better in that regard.
  - lispm 8y ago
    > that all schemes provide their own lower level macro facility and that all schemes provide their own lower level macro facility ... or the equivalent of Lisp's DEFMACRO. There are tons of options. But it's a bit disappointing that such a central feature hasn't found acceptance of a main solution in the Scheme world. R7RS small has only syntax-rules AFAIK, and something like syntax-case is planned (?) for the R7RS large (which does not yet exist, AFAIK). It's not even clear to me whether 'syntax-case' is universally seen as 'solved problem'. Anyone who has a basic idea of Scheme should know that syntax-rules is not the only option - a short look into a manual of an existing Scheme implementation should be sufficient...
    - bjoli 8y ago
      Not quite, the low level macro facility provides hygiene as well (well, maybe not explicit renaming macros) with the ability to break hygiene when desired. These systems can be used to implement an unhygienic macro system (iirc, my defmacro about 7 lines, including the syntax case boilerplate). R6RS standardised syntax-case, so any r6rs scheme already has it, but due to many things r6rs was a huge controversy and many implementations never started using it. Guile, chez, racket, Kawa, jscheme, larceny all support it. I expect syntax case in one form or another to make it into r7rs large, but you never know. Lots of cool things are making its way into r7rs large, including HAMT-based maps. There must of course be a vote, but that is just too good to not have :)

by bjoli 8y ago

gpderetta 8y ago

That's intersting, because the lisp 'the right thing' approach [1] calls for correctness and ease of use over simplicity of implementation. [1] as opposed to the alledged 'worse is better' of the unix world.

bjoli 8y ago
It is a matter of preference. Sometimes you end up using gensym in scheme as well, especially for introducing identifiers in bulk.

lispm 8y ago

> uniformly believe that syntax-rules is the only macro facility far from it. CLers know that Scheme has zillions of different macro systems. Which makes the whole topic highly confusing and intellectually interesting.

bjoli 8y ago
What I meant by that is that CLers usually complain about hygiene as if it was impossible to break. I don't know how many times I have had to explain that syntax-rules is the high level macro facility and that all schemes provide their own lower level macro facility, be it explicit/implicit renaming (chicken), syntax-case (r6rs) or syntactic closures (Chibi?). I understand the complaint that this isn't portable. It isn't. R6RS tried to standardise it. Hopefully r7rs does better in that regard.
- lispm 8y ago
  > that all schemes provide their own lower level macro facility and that all schemes provide their own lower level macro facility ... or the equivalent of Lisp's DEFMACRO. There are tons of options. But it's a bit disappointing that such a central feature hasn't found acceptance of a main solution in the Scheme world. R7RS small has only syntax-rules AFAIK, and something like syntax-case is planned (?) for the R7RS large (which does not yet exist, AFAIK). It's not even clear to me whether 'syntax-case' is universally seen as 'solved problem'. Anyone who has a basic idea of Scheme should know that syntax-rules is not the only option - a short look into a manual of an existing Scheme implementation should be sufficient...
  - bjoli 8y ago
    Not quite, the low level macro facility provides hygiene as well (well, maybe not explicit renaming macros) with the ability to break hygiene when desired. These systems can be used to implement an unhygienic macro system (iirc, my defmacro about 7 lines, including the syntax case boilerplate). R6RS standardised syntax-case, so any r6rs scheme already has it, but due to many things r6rs was a huge controversy and many implementations never started using it. Guile, chez, racket, Kawa, jscheme, larceny all support it. I expect syntax case in one form or another to make it into r7rs large, but you never know. Lots of cool things are making its way into r7rs large, including HAMT-based maps. There must of course be a vote, but that is just too good to not have :)