#12807: Taking the real part of a sum of exponentials with imaginary exponents
gives wrong result
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Reporter: inaki | Owner: burcin
Type: defect | Status: new
Priority: major | Milestone: sage-6.4
Component: symbolics | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Comment (by kcrisman):
This gets really weird, actually.
{{{
sage: a.real()
-1/2
sage: b.real()
1/2
sage: (a-b).real() # good
-1
sage: (a-2*b).real() # good
-3/2
sage: (a-3*b).real() # ho-hum
-2
sage: (2*a-b).real() # yikes
1/2
sage: (3*a-b).real() # what?
3/4
sage: (4*a-b).real() # consistent...
1
sage: (5*a-b).real() # ?!?!?
5/4
sage: (-a-b).real() # seeing but not believing
-1/4
sage: (-2*a-b).real()
-1/2
sage: (-3*a-b).real()
-3/4
sage: (2*a).real() # okay
-1
sage: (2*a+b).real() # okay
-1/2
sage: (3*a+b).real()
-1
sage: (4*a+b).real()
-3/2
}}}
This is consistent with Pynac somehow thinking that `a.real()==1/4` when
preceded by a positive constant and `-1/4` when given a negative constant.
But only when part of a sum including `-b`, with `+b` it's fine.
I tried to figure out what it was but so far no luck.
--
Ticket URL: <http://trac.sagemath.org/ticket/12807#comment:6>
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