[racket] export/import problem, and how to debug

Ya, the documentation says:

"The syntax of require-spec can be extended via define-require-syntax
... . The pre-defined forms (as exported by racket/base) are as
follows:"

and then lists, among other things, 'rename-in'

I think the 'as exported' is the closest thing to a clue to someone
who doesn't know about how extensible syntax transformers work that
the 'require' macro is going to look for these *bindings* not these
*symbols*.

Jay

On Tue, Aug 3, 2010 at 12:25 PM, Shriram Krishnamurthi <sk at cs.brown.edu> wrote:
> I see: each of these is a *separate* macro!  That clarifies it.  Thanks.
>
> On Tue, Aug 3, 2010 at 2:22 PM, Jay McCarthy <jay.mccarthy at gmail.com> wrote:
>> You didn't provide rename-in (etc).
>>
>> You need to provide all the require/provide transformers you want.
>>
>> Jay
>>
>> On Tue, Aug 3, 2010 at 12:13 PM, Shriram Krishnamurthi <sk at cs.brown.edu> wrote:
>>> Let me see if I can reduce my problem to the simplest case.  Here is a
>>> program that works fine:
>>>
>>> -----
>>> #lang racket
>>> (require (rename-in racket/tcp
>>>                        (tcp-accept accept)
>>>                        (tcp-listen listen)))
>>> -----
>>>
>>> (It's from the docs, and it works as you would expect.  I only say all
>>> this to say I've checked the syntax of this expression.)
>>>
>>> This is illegal in ASL:
>>>
>>> -----
>>> #lang s-exp lang/htdp-advanced
>>> (require (rename-in racket/tcp
>>>                        (tcp-accept accept)
>>>                        (tcp-listen listen)))
>>> -----
>>>
>>>  require: expected a module name as a string, a `lib' form, or a
>>>  `planet' form, found something else in: (rename-in racket/tcp
>>>  (tcp-accept accept) (tcp-listen listen))
>>>
>>> [Same error if I use the (module ...) form at the REPL.]
>>>
>>> Let's say I want to give students access to require-on-steroids.  So I
>>> define this language (sk-test-lang.rkt):
>>>
>>> -----
>>> #lang racket
>>> (require [except-in lang/htdp-advanced require])
>>> (provide require
>>>         [except-out (all-from-out lang/htdp-advanced)])
>>> -----
>>>
>>> When I check syntax and highlight "require" on the provide line, the
>>> arrow points to "racket".  Great.
>>>
>>> Now I try to use this.  First I'll do something simple (and you'll see
>>> why in a moment):
>>>
>>> -----
>>> #lang s-exp "sk-test-lang.rkt"
>>> (require "lib.rkt")
>>> -----
>>>
>>> This works fine, importing what lib.rkt provides.  When I check
>>> syntax, the "require" comes from "sk-test-lang.rkt".  This hopefully
>>> means that by transitivity, require comes from racket.
>>>
>>> So now I try this:
>>>
>>> -----
>>> #lang s-exp "sk-test-lang.rkt"
>>> (require (rename-in racket/tcp
>>>                        (tcp-accept accept)
>>>                        (tcp-listen listen)))
>>> -----
>>>
>>> But I get
>>>
>>>  rename-in: not a require sub-form in: (rename-in racket/tcp
>>>  (tcp-accept accept) (tcp-listen listen))
>>>
>>> The thing that boggles my mind is that this error message is NEITHER
>>> the one that you would get from racket itself (since this is not an
>>> error in racket), NOR the one from ASL (since I've shown you the error
>>> text above).
>>>
>>> So:
>>>
>>> 1. Where is require coming from?
>>>
>>> 2. How could I go about figuring this for myself?  (The macro stepper
>>> doesn't seem useful, or at least I don't see how to use it here.)
>>>
>>> 3. How do I fix my program? (-:
>>>
>>> Shriram
>>> _________________________________________________
>>>  For list-related administrative tasks:
>>>  http://lists.racket-lang.org/listinfo/users
>>>
>>
>>
>>
>> --
>> Jay McCarthy <jay at cs.byu.edu>
>> Assistant Professor / Brigham Young University
>> http://teammccarthy.org/jay
>>
>> "The glory of God is Intelligence" - D&C 93
>>
>



-- 
Jay McCarthy <jay at cs.byu.edu>
Assistant Professor / Brigham Young University
http://teammccarthy.org/jay

"The glory of God is Intelligence" - D&C 93