#11590: Integrating the sgn() function can produce incorrect results
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Reporter: mjo | Owner: burcin
Type: defect | Status: new
Priority: major | Milestone:
Component: calculus | Keywords:
Work_issues: | Upstream: Reported upstream. Developers
acknowledge bug.
Reviewer: | Author:
Merged: | Dependencies:
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Comment(by mjo):
I'm stumped on this one. We get the correct antiderivative:
{{{
sage: integrate(x*sgn(x^2-1/4),x)
1/2*abs(x^2 - 1/4)
}}}
And ECL gives us the right answer, so it's not an environment setting:
{{{
sage: from sage.interfaces.maxima_lib import ecl_eval
sage: ecl_eval("#$'integrate(x*signum(x^2-1/4),x,-1,0);$")
<ECL: ((RAT SIMP) -1 4)>
}}}
But going through `maxima_eval` is still trouble:
{{{
sage: integrate(x*sgn(x^2-1/4),x,-1,0)
1/2
sage: from sage.interfaces.maxima_lib import maxima_eval
sage: a = '($INTEGRATE ((MTIMES SIMP) $X ((%SIGNUM SIMP) ((MPLUS SIMP)
((RAT SIMP) (- 1) 4) ((MEXPT SIMP) $X 2))) ) $X -1 0)'
sage: maxima_eval(a)
<ECL: ((RAT SIMP) 1 2)>
}}}
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11590#comment:4>
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