TypeError: cannot evaluate symbolic expresssion numerically

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ma...@mendelu.cz

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Mar 7, 2010, 9:54:26 AM3/7/10
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Dear support

when I worked on trac http://trac.sagemath.org/sage_trac/ticket/8459
(which has been motivated by [1]) I got problems with parsing
expressions

With patch for #8459 I get the following (note that the function g(x)
cannot be evaluated numerically, unless I use eval, preparse and
_repr_ )

Can you help me to solve this problem? Thanks.

Robert Marik

----------------------------------------------------------------------
| Sage Version 4.3.3, Release Date: 2010-02-21 |
| Type notebook() for the GUI, and license() for information. |
----------------------------------------------------------------------
Loading Sage library. Current Mercurial branch is: polylog
sage: g(x)=integrate(ln(1-x^2)/x,x)
sage: g(1/2).n()
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)

/opt/sage-4.3.3/<ipython console> in <module>()

/opt/sage-4.3.3/local/lib/python2.6/site-packages/sage/symbolic/
expression.so in
sage.symbolic.expression.Expression.n (sage/symbolic/expression.cpp:
17036)()

TypeError: cannot evaluate symbolic expresssion numerically
sage: g(x)=eval(preparse(integrate(ln(1-x^2)/x,x)._repr_()))
sage: g(1/2).n()
0.688640713882747
sage: g
x |--> log(-x^2 + 1)*log(x) + 1/2*polylog(2, -x^2 + 1)


-----------------------
[1] http://groups.google.cz/group/sage-support/browse_thread/thread/513d8072be409669

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