CHICKEN Scheme

Summary

Chicken allows for shadowing syntax in a way disallowed by R5RS/sec.5.3

Metadata

Id: 17e2c4519ae003bf9ee0a6b8bf8db6d5237f9789
Trac id: 209
Type: task
Reporter: jeronimo
Owner: felix
Cc: ashinn
Status: closed
Component: expander
Estimated difficulty:
Resolution: fixed
Priority: minor
Milestone:
Version: 4.5.x
Changetime: 2011-04-04 08:31:00 UTC
Created: 2010-04-10 19:57:38 UTC
Keywords:

Description

Hi,

With master/HEAD, (latest commit is 8acb3f92df82f369fc5dbef8f7c44a68468a92c3):

 #;7> (define define (lambda () 'z))
 #;8> define
 #<procedure (define)>
 #;9> (define)
 
 Error: (car) during expansion of (define ...) - bad argument type: ()
 
     Call history:
 
     <syntax>        (define)    <-- 
 #;9> (let ((a define)) (a))
 z
 #;10>

But section 5.3 of R5RS explicitly disallows defining define among other things (it mentions "(define define 3)" as an example of error, and Chicken allows it).

This is not listed in the "Deviations form the standard" section of the manual, so it's not clear if it's a bug or an intended deviation.

P.S.: Bigloo does the same; Chibi signals an error; Guile shadows the define syntax even when it's in procedure-calling position: "(define)" above works in Guile and returns the symbol z!

Changes and comments

[2010-04-13 13:48:33 UTC] felix wrote:

Yes, this is an error, but the implementation is free to handle it in whatever way it likes (at least that is my understanding of the term "is an error").

I will add a note to the manual that describes the current behaviour.