[racket] How to make an identifier that will have a certain binding no matter what phase level it's referenced at?

On Jul 27, 2014, at 1:20 PM, Roman Klochkov <kalimehtar at mail.ru> wrote:

> It is bound to racket/base lambda. More correct, phase0 lambda in racket/base.
> But when you call it in level 2, there are no level 0 lambda.
> 
> Minimal similar test-case:
> ---------------
> (module m racket/base
>   (provide test-stx)
> 
;; what you need here is this:
(require (for-template racket/base))
>   (define (test-stx) #'(lambda (x) x)))
> 
> (require (for-syntax 'm))
> 
> (define-syntax (test stx) (test-stx))
> 
> test
> 

Then it works fine.  But since #λ is a reader extension, not a macro, it could be at any phase level.  
I was wondering if there’s any way to construct an identifier that would be bound to lambda from racket/base
no matter what phase level it’s referenced at.  
These examples with macros only have to make sure that it’s there at the for-template phase level relative to test-stx.  
A reader extension doesn’t have that constraint.  
> 
> . lambda: unbound identifier;
>  also, no #%app syntax transformer is bound in: lambda
> ----------------
> 
> Minimal correct case:
> ------------------
> (module m racket/base
>   (provide test-stx)
>   (define (test-stx a l)
>     (with-syntax ([#%app a]
>                   [lambda l])
>       #'(lambda (x) x))))
> 
> (require (for-syntax 'm))
> 
> (define-syntax (test stx) (test-stx #'#%app #'lambda))
> 
> test
> --------------------
> 
> So you have to somehow give correct #'lambda and #'#%app into your macros.
> 
> 
> Sun, 27 Jul 2014 12:21:36 -0400 от "Alexander D. Knauth" <alexander at knauth.org>:
> 
> I just tried to try it and see if it worked, when I realized that it won’t work because I can’t use quote-syntax.  
> 
> Is there any way to get around that?  And would it even work anyway?  
> 
> On Jul 27, 2014, at 6:59 AM, Roman Klochkov <kalimehtar at mail.ru> wrote:
> 
>> Maybe via "Cross-Phase Persistent Module Declarations" http://docs.racket-lang.org/reference/syntax-model.html#%28part._cross-phase._persistent-grammar%29 ?
>> 
>> 
>> Thu, 24 Jul 2014 21:24:20 -0400 от "Alexander D. Knauth" <alexander at knauth.org>:
>> How can I make an identifier that will have a certain binding no matter what phase level it's referenced at?
>> 
>> For example if I’m making a reader extension that will produce a lambda expression, how do I make it so that the lambda expression will be able to exist at any phase level?
>> 
>> For example this program using #lang rackjure doesn’t work:
>> #lang rackjure
>> (require (for-meta 1 racket/base)
>>          (for-meta 2 racket/base)
>>          (for-meta 3 racket/base)
>>          (for-meta 4 racket/base)
>>          )
>>                                                                                              
>> #λ(* 2 %) ; works, produces approx. (lambda (%) (* 2 %))
>> (begin-for-syntax
>>   (begin-for-syntax
>>     #λ(* 2 %) ; lambda: unbound identifier at phase 2;
>>     ;         ;   also, no #%app syntax transformer is bound in: lambda
>>     ))
>> 
>> Is there any way to construct an identifier that would be bound to lambda from racket/base no matter what phase level it’s used in?
>> 
>> 
>> ____________________
>>   Racket Users list:
>>   http://lists.racket-lang.org/users
>> 
>> 
>> 
>> -- 
>> Roman Klochkov
> 
> 
> 
> -- 
> Roman Klochkov

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