unbound variable detection

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2 total messages Started by Kardan Kaveh Fri, 22 Jan 1993 04:46

#196

Author: Kardan Kaveh
Date: Fri, 22 Jan 1993 04:46

20 lines
794 bytes

Is it possible to tell if a given variable is undefined?

For example, something along the lines of:

(define x 3)

(bound? x) --> #t

(bound? y) --> #f

Thanks,

Kaveh


-- 
------------
Kaveh Kardan                                       kaveh@taarna.UUCP
Systeme Taarna                                     kardank@eole.umontreal.qc.ca
Montreal Quebec Canada                             (514)844-8448

Re: unbound variable detection

#199

Author: Guillermo J. Rozas
Date: Fri, 22 Jan 1993 16:57

25 lines
1233 bytes

In article <1993Jan22.044623.19581@cc.umontreal.ca> kardank@ERE.UMontreal.CA (Kardan Kaveh) writes:

|   From: kardank@ERE.UMontreal.CA (Kardan Kaveh)
|   Newsgroups: comp.lang.scheme.c
|   Date: 22 Jan 93 04:46:23 GMT
|
|   Is it possible to tell if a given variable is undefined?
|
|   For example, something along the lines of:
|
|   (define x 3)
|
|   (bound? x) --> #t
|
|   (bound? y) --> #f

(define-macro (bound? name)
  `(not (lexical-unbound? (the-environment) ',name)))

or

(define-macro (bound? name)
  `(not (lexical-unbound? user-initial-environment ',name)))

depending on exactly what you want.

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