[Maxima-bugs] [ maxima-Bugs-767401 ] Some problems with featurep/complex

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Bugs item #767401, was opened at 2003-07-07 16:26
Message generated for change (Settings changed) made by robert_dodier
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>Category: Lisp Core - Assume
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Stavros Macrakis (macrakis)
Assigned to: Nobody/Anonymous (nobody)
Summary: Some problems with featurep/complex

Initial Comment:
  declare(rrr,real)
  declare(zzz,complex)

featurep(x,real) => false (!!)
With domain=real, should be true.

featurep(%i,imaginary) => false (!!)
Should be true.

featurep(cabs(zzz),real) unnecessarily asks whether 
SQRT(REALPART(zzz)^2+IMAGPART(zzz)^2) is positive 
or zero; similarly for sqrt(abs(x)+abs(y)).

Though featurep(sqrt(x),real) asks x pos/neg/z and 
gives correct results, featurep(sqrt(x),imaginary) doesn't 
ask the questions and returns false.

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Note that (as best I understand its semantics), featurep 
*correctly* gives featurep(rrr,complex)=>true, etc.  I 
believe that featurep is supposed to report whether the 
range of values of an expression is a subset of the set 
defined.  Since rrr is real, and the reals are a subset of 
the complexes, 3 is also complex.


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