[Maxima-bugs] [ maxima-Bugs-711472 ] Strings mishandled in constantp, orderlessp, comparison

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Bugs item #711472, was opened at 2003-03-28 10:59
Message generated for change (Settings changed) made by robert_dodier
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>Category: Lisp Core
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Stavros Macrakis (macrakis)
Assigned to: Nobody/Anonymous (nobody)
Summary: Strings mishandled in constantp, orderlessp, comparison

Initial Comment:
Most parts of Maxima incorrectly treat Maxima strings 
(e.g. "foo") as variables, not as manifest constants.  
This is understandable, since they are represented 
internally as Lisp symbols, but is still incorrect.

A few places get it right.  For example, setting a string 
to a value ("f":3) gives an error.  But note that mset 
doesn't even use the standard mstringp predicate....

In many places, the problem with strings is simply that 
illegal operations don't give errors, e.g. depends("f",g).

But in other places, meaningful operations give incorrect 
answers:

constantp("foo") => false BAD
  This is easy to fix, and the runtime overhead shouldn't 
be an issue nowadays.  Though perhaps it would be 
better to give string symbols an explicit plist property.

orderlessp(foo,"foo") => true, though the convention is 
that all manifest constants come before variables.  Cf.
sort([2,%pi,foo,"foo"]) => [2,%PI,foo,"foo"]

Probably the biggest problematic area is in 
comparisons.  Since string comparisons don't work, 
strings become pretty useless in Maxima programming.

The following comparisons give errors:

is("a"<"b")
is("a"<="b")
is("a" # "b")
is(equal("a","b"))

Though the following predicates work correctly:

is("a"="a") => true
is("a"="b") => false
is("a" # "a") => false
is("a" # "b") => true
is("a"<="a") => true
is(equal("a","a")) => true

Not by coincidence, the correct cases are those where 
the rules for variables give the correct result....

Of course, it would be better to convert Maxima strings 
to use Lisp strings, but in the meantime....  Note, by the 
way, that Maxima DOES depend on the fact that strings 
are interned to do things like put the OPR property on 
&+.  But this can of course be fixed.

Maxima 5.9.0 GCL 2.5.0 mingw32 Windows 2000


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