#16587: evaluation of sgn(expr) fails
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Reporter: rws | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.3
Component: symbolics | Keywords: sgn, evaluation
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
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As reported in http://ask.sagemath.org/question/8535/problem-with-sign-
sgn-and-n/ by Louis Cypher:
{{{
sage: M = sgn(cos(3/2))
sage: M.n()
TypeError Traceback (most recent call
last)
<ipython-input-5-0f11e9bd1e87> in <module>()
----> 1 M.n()
/home/ralf/sage/local/lib/python2.7/site-
packages/sage/symbolic/expression.so in
sage.symbolic.expression.Expression._numerical_approx
(build/cythonized/sage/symbolic/expression.cpp:24086)()
TypeError: cannot evaluate symbolic expression numerically
}}}
kcrisman:
Problem seems to be that in `M.n??` we see that it's looking for
`is_a_numeric(x._gobj)` but apparently that fails, as does the constant,
so it thinks we are looking at evaluating `sgn(cos(x))` instead of
`sgn(cos(3/2))`.
--
Ticket URL: <http://trac.sagemath.org/ticket/16587>
Sage <http://www.sagemath.org>
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