#8752: Can't evaluate numerically symbolic expression resulting from integral().
------------------------+---------------------------------------------------
Reporter: lfousse | Owner: burcin
Type: defect | Status: new
Priority: major | Milestone:
Component: calculus | Keywords: integral, numerical conversion
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Consider the following (in sage 4.3.5):
{{{
sage: integral(exp(-x^2), x, 17, 42)
-1/2*sqrt(pi)*erf(17) + 1/2*sqrt(pi)*erf(42)
sage: N(-1/2*sqrt(pi)*erf(17) + 1/2*sqrt(pi)*erf(42))
0.000000000000000
}}}
But:
{{{
sage: N(integral(exp(-x^2), x, 17, 42))
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
/opt/sage-4.3.5/<ipython console> in <module>()
/opt/sage-4.3.5/local/lib/python2.6/site-packages/sage/misc/functional.pyc
in numerical_approx(x, prec, digits)
1161 prec = int((digits+1) * 3.32192) + 1
1162 try:
-> 1163 return x.numerical_approx(prec)
1164 except AttributeError:
1165 from sage.rings.complex_double import
is_ComplexDoubleElement
/opt/sage-4.3.5/local/lib/python2.6/site-
packages/sage/symbolic/expression.so in
sage.symbolic.expression.Expression.n
(sage/symbolic/expression.cpp:17043)()
TypeError: cannot evaluate symbolic expression numerically
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8752>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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