[racket-dev] problem with require and frtime

Greg, how difficult would it be to migrate frtime to #lang racket? -- Matthias



On Jan 19, 2012, at 8:13 AM, Matthew Flatt wrote:

> The `frtime' language exports an `=' that isn't the same as `=' in
> `racket', so that's why the pattern doesn't match. (This seems like a
> further weakness of the `frtime' docs to specify the exports
> precisely.)
> 
> You could avoid bound names like `=' as literals in the macro.
> Normally, it works best for a form-exporting macro to also export
> bindings for any literals in the form. Otherwise, this kind of
> confusion is common.
> 
> Alternatively, you may want to match literals in your macro
> symbolically instead of by binding. You can't do that easily with
> `syntax-rules', but you can use `syntax-case*' and supply `(lambda (a
> b) (eq? (syntax-e a) (syntax-e b)))' as the literal-comparison
> function.
> 
> If it were me and I decided to go in the direction of symbol equality,
> I'd use keywords instead --- `#:?' and `#:=' instead of `?' and `=' ---
> which makes clear that there's no question of binding.
> 
> 
> At Thu, 19 Jan 2012 10:46:37 +0100, Marijn wrote:
>> On 18-01-12 17:47, Matthew Flatt wrote:
>>> At Wed, 18 Jan 2012 12:02:10 +0100, Marijn wrote:
>>>> I would expect both forms to work. This is a reduction of a different
>>>> problem possibly caused by these issues here.
>> 
>> So I tried to cut down my program to a reasonably sized test-case which
>> is attached to this email. model.rkt contains (what's left of) the model
>> macro, demo1.rkt contains a small model and a (require frtime). If you
>> do "racket demo1.rkt" then you get the following error:
>> 
>> 
>> model.rkt:30:17: make-entry: bad syntax in: (make-entry (= profit
>> (for/hash ((y years)) (values y (- (hash-ref income y 0) (hash-ref
>> expenses y 0))))) (years income expenses profit))
>> 
>> === context ===
>> standard-module-name-resolver
>> 
>> 
>> but if you comment the (require frtime) then the error goes away. I have
>> other code that tests this same simple-economy model with the
>> non-cutdown version of the model macro and supporting code and
>> everything seems to work fine.
>> 
>> Any idea what's going on here?
>> 
>> Marijn
>> 
>> ------------------------------------------------------------------------------
>> [text/plain "demo1.rkt"] [~/Desktop & open] [~/Temp & open]
>> 
>> ------------------------------------------------------------------------------
>> [text/plain "model.rkt"] [~/Desktop & open] [~/Temp & open]
>> 
>> ------------------------------------------------------------------------------
>> [application/pgp-signature "signature.asc"] [~/Desktop & open] [~/Temp & open]
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