4 ms·

A Scheme syntax-rules primer (2008)

56 points by mac01021 7y ago

amirouche 7y ago
very useful resource, I recommend it.
neilv 7y ago
Another one is Joe Marshall's "syntax-rules Primer for the Merely Eccentric": http://sites.google.com/site/evalapply/eccentric.txt http://sites.google.com/site/evalapply/eccentric.txt Today, instead of `syntax-rules`, you'll probably use `syntax-case`, which is a lot easier to use for harder purposes, and also easier error-checking, just not as interesting as `syntax-rules`. Or, if you're using Racket, `syntax-parse`. Greg Hendershott's "Fear of Macros" should be an easy introduction to some of the newer ways, though it has some Racket-specific bits in it: https://www.greghendershott.com/fear-of-macros/ https://www.greghendershott.com/fear-of-macros/
- widdershins 7y ago
  I still use `syntax-rules` a lot for simple macros - there's hardly any boilerplate and macros come out very readable without all the quasi-quoting, quasi-unquoting etc. that happens in other macro systems. But some things just can't be accomplished with it. I only turn to `syntax-case` for these things, like introducing new identifiers, or fully procedural tasks. It blew my mind when I discovered that I could write a macro that actually reads files from disk and binds variables to each path at macro-expansion time (not saying that's a great idea though...)
  - neilv 7y ago
    I like `syntax-rules` and have done some crazy things with it. If I were going to teach someone syntax extension in Scheme or Racket, however, I'd just use `syntax-case` or `syntax-parse` for everything. That avoids confusing people with two different languages.
mehrdadn 7y ago
Confused, why is the macro name necessary when the pattern itself already specifies the macro name?
- kryptiskt 7y ago
  Making define-syntax bind to a name that appears in the body would be confusing. You can omit the macro name in the pattern and use an underscore instead.
  - mehrdadn 7y ago
    Does the name have any significance at all? The apparent lack of it is far more confusing...
deleted 7y ago
[deleted]
camoy 7y ago
If you're in Racket consider using syntax-parse instead. It's syntax-rules/syntax-case's more capable cousin: https://www2.ccs.neu.edu/racket/pubs/icfp10-cf.pdf https://www2.ccs.neu.edu/racket/pubs/icfp10-cf.pdf
norswap 7y ago
Cool! I'd love a follow-up that shows how syntax-rules can do things that are out of reach for something like the C macro preprocessor.

56 points by mac01021 7y ago

very useful resource, I recommend it.

Another one is Joe Marshall's "syntax-rules Primer for the Merely Eccentric": http://sites.google.com/site/evalapply/eccentric.txt http://sites.google.com/site/evalapply/eccentric.txt Today, instead of `syntax-rules`, you'll probably use `syntax-case`, which is a lot easier to use for harder purposes, and also easier error-checking, just not as interesting as `syntax-rules`. Or, if you're using Racket, `syntax-parse`. Greg Hendershott's "Fear of Macros" should be an easy introduction to some of the newer ways, though it has some Racket-specific bits in it: https://www.greghendershott.com/fear-of-macros/ https://www.greghendershott.com/fear-of-macros/

widdershins 7y ago
I still use `syntax-rules` a lot for simple macros - there's hardly any boilerplate and macros come out very readable without all the quasi-quoting, quasi-unquoting etc. that happens in other macro systems. But some things just can't be accomplished with it. I only turn to `syntax-case` for these things, like introducing new identifiers, or fully procedural tasks. It blew my mind when I discovered that I could write a macro that actually reads files from disk and binds variables to each path at macro-expansion time (not saying that's a great idea though...)
- neilv 7y ago
  I like `syntax-rules` and have done some crazy things with it. If I were going to teach someone syntax extension in Scheme or Racket, however, I'd just use `syntax-case` or `syntax-parse` for everything. That avoids confusing people with two different languages.

mehrdadn 7y ago

Confused, why is the macro name necessary when the pattern itself already specifies the macro name?

kryptiskt 7y ago
Making define-syntax bind to a name that appears in the body would be confusing. You can omit the macro name in the pattern and use an underscore instead.
- mehrdadn 7y ago
  Does the name have any significance at all? The apparent lack of it is far more confusing...

deleted 7y ago

[deleted]

camoy 7y ago

If you're in Racket consider using syntax-parse instead. It's syntax-rules/syntax-case's more capable cousin: https://www2.ccs.neu.edu/racket/pubs/icfp10-cf.pdf https://www2.ccs.neu.edu/racket/pubs/icfp10-cf.pdf

norswap 7y ago

Cool! I'd love a follow-up that shows how syntax-rules can do things that are out of reach for something like the C macro preprocessor.