Bugs item #3075478, was opened at 20100925 14:31
Message generated for change (Comment added) made by crategus
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Category: None
Group: None
>Status: Closed
>Resolution: Fixed
Priority: 5
Private: No
Submitted By: Barton Willis (willisbl)
Assigned to: Nobody/Anonymous (nobody)
Summary: is(equal(abs(%i * z + 1),z%i));
Initial Comment:
Should be unknown, not false:
(%i6) is(equal(abs(%i * z + 1),z%i));
(%o6) false
The expressions are equal when z = %i.
(%i8) subst(z=%i, abs(%i * z + 1)=z%i);
(%o8) 0=0
This is rtest_equal #63  the expected answer is wrong, I think.

>Comment By: Dieter Kaiser (crategus)
Date: 20101002 14:42
Message:
Because of revision 1.77 of compar.lisp the example works as expected:
(%i1) is(equal(abs(%i * z + 1),z%i));
(%o1) unknown
Closing this bug report as fixed.
Dieter Kaiser

Comment By: Dieter Kaiser (crategus)
Date: 20100925 17:15
Message:
I think the handling of complex and real expression and symbols is
confusing at a lot of places. If we declare a complex or an imaginary
symbol the test of this bug report gives the expected results:
(%i1) declare(z,complex, j,imaginary)$
(%i3) is(equal(abs(%i*z+1),z+%i));
(%o3) unknown
(%i4) is(equal(abs(%i*j+1),j+%i));
(%o4) unknown
A symbol not declared to be complex or imaginary is assumed to be real.
With this assumption the following test might be called correct too. The
symbol x can not have the value %i, it is assumed to be real:
(%i5) is(equal(abs(%i*x+1),x+%i));
(%o5) false
The problem is that the assumption, that any symbol is real by default
sometimes gives the desired results, sometimes not.
By the way: The option variable domain does not change anything. This is a
problem too. I think a clear concept is missing to get all this right.
Dieter Kaiser

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