[racket-dev] Identifier macros

I think two additions/refinements would be good here: 

1. The section on identifier macros in the Guide (16.1.5) should mention that define-syntax introduces short-hands for identifiers, period. That is, the following interaction works perfectly fine: 

 > (define-syntax (foo stx) #'7)
 > (+ foo 2)
 9
 > foo
 7

2. Then the section should explain that it is the use of syntax-rule/syntax-rules/syntax-case/syntax-parse that forces stx to be in a certain shape. If foo is not defined with any of these features, the identifier alone triggers an expansion. 

So, when define-syntax demands the use of syntax-parse (or friends) but you also want to use this identifier with a related meaning in an identifier position, you should use syntax-id-rules. 

Does this make sense? -- Matthias








On Dec 5, 2012, at 7:23 AM, Matthew Flatt wrote:

> I'd like to improve the documentation, but I can't tell which part
> you're talking about. (The only place where I can find "identifier
> macros" is in the Guide, but that's about `syntax-rules' versus
> `syntax-id-rules'.) Can you point to the part that you're reading and
> the specific text that seems misleading?
> 
> At Tue, 4 Dec 2012 17:16:17 -0500, Carl Eastlund wrote:
>> I'm confused about so-called "identifier macros".  I had thought that
>> ordinary transformers bound to functions could only transform
>> application-position references to themselves, and that a "set!
>> transformer" was required to transform bare references and set!
>> references.  Turns out I was wrong, set! transformers are in fact only
>> required to transform set! references.  So why are they listed under the
>> documentation for "identifier macros" and why does that documentation imply
>> that normal transformers can't handle bare references?
>> 
>> Carl Eastlund
>> _________________________
>>  Racket Developers list:
>>  http://lists.racket-lang.org/dev
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>  Racket Developers list:
>  http://lists.racket-lang.org/dev

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