[racket-dev] provide expand-clause in racket/private/for.rkt

From: Stephen Chang (stchang at ccs.neu.edu)
Date: Fri Sep 6 14:44:20 EDT 2013

On Fri, Sep 6, 2013 at 7:54 AM, Matthew Flatt <mflatt at cs.utah.edu> wrote:
> As far as I can see, exporting `expand-clause` is ok.
> Ideally, I think it should be exported from a new
> `racket/for-transform` library, instead of used directly from
> `racket/private/for`. Also, `expand-for-clause` might be a better name.

Ok I will add it. Thanks.

> At Fri, 6 Sep 2013 00:45:40 -0400, Stephen Chang wrote:
>> Hi dev,
>> I would like to provide (for-syntax) the "expand-clause" function in
>> racket/private/for.rkt. Would this cause any problems? Would anyone
>> object to this?
>> I have an implementation of for/X in my generic-bind library that uses
>> expand-clause and with it, the generic-bind ~for forms are as fast,
>> sometimes a little faster, than racket's for/X in some preliminary
>> testing. (Without access to expand-clause, sequence traversal is slow
>> --- the current planet-available version of my library uses
>> sequence-generate and is twice as slow.)
>> The "sometimes a little faster" is likely in part due to less
>> error-checking, but my implementation passes all the for/X unit tests
>> and so as is, it can reasonably be used in place of for/X.
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