[Maxima-bugs] [ maxima-Bugs-705734 ] [a,b,c][0] => "["

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Bugs item #705734, was opened at 2003-03-18 10:42
Message generated for change (Comment added) made by robert_dodier
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>Category: Lisp Core
Group: None
>Status: Closed
>Resolution: Fixed
Priority: 5
Submitted By: Stavros Macrakis (macrakis)
Assigned to: Nobody/Anonymous (nobody)
>Summary: [a,b,c][0] => "["

Initial Comment:
[a,b,c][0] => "["    --- should be an error

foo:[a,b,c]$ foo[0] => "["      --- same

The subscript operator should select the nth element of 
a list-like object.  It should NOT select the nth 
component of a structure -- that is what part/inpart is for.

After all, (a+b)[0] is not "+".  Similarly, [a,b][0] should 
not be "[", but an error.

Currently, meval uses inpart for subscripting; this code 
needs to be corrected.

5.9.0, GCL, Windows


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>Comment By: Robert Dodier (robert_dodier)
Date: 2006-07-04 11:02

Message:
Logged In: YES 
user_id=501686

Following patch committed as r1.27 src/mlisp.lisp. This is
in MAPPLY1. Now [a,b,c][0] => error message. Closing this
report as fixed.

diff -u -r1.26 mlisp.lisp
--- mlisp.lisp  15 Feb 2006 16:44:29 -0000      1.26
+++ mlisp.lisp  4 Jul 2006 16:56:29 -0000
@@ -155,6 +155,8 @@
      (if (not (or (= (length args) 1)
                  (and (eq (caar fn) '$matrix) (= (length
args) 2))))
         (merror "Wrong number of indices:~%~M" (cons
'(mlist) args)))
+     (if (memq 0 args)
+       (merror "No such ~M element: ~M~%" (if (eq (caar fn)
'mlist) "list" "matrix") `((mlist) ,@args)))
      (do ((args1 args (cdr args1)))
         ((null args1) (let (($piece $piece) ($partswitch
'mapply))
                         (apply #'$inpart (cons fn args))))


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