I get different results from Sage when I try to get a numerical
approximation for an expression and if I use evaluate a preparse of the
string. I get different results on different versions of sage as well. Here
are samples:
----------------------------------------------------------------------
| Sage Version 5.3, Release Date: 2012-09-08 |
| Type "notebook()" for the browser-based notebook interface. |
| Type "help()" for help. |
----------------------------------------------------------------------
sage: eval(preparse("numerical_approx(integral(x/(x^3-x+1), x, 1, 2))"))
0.132008722884722
sage: numerical_approx(integral(x/(x^3-x+1), x, 1, 2))
0.132008722884722
sage: A = integral(x/(x^3-x+1), x, 1, 2)
sage: A_str = str(A)
sage: eval(preparse("numerical_approx("+A_str +")"))
-0.393296585552547
sage:
┌────────────────────────────────────────────────────────────────────┐
│ Sage Version 6.5, Release Date: 2015-02-17 │
│ Type "notebook()" for the browser-based notebook interface. │
│ Type "help()" for help. │
└────────────────────────────────────────────────────────────────────┘
sage: eval(preparse("numerical_approx(integral(x/(x^3-x+1), x, 1, 2))"))
1.45943044687563
sage: numerical_approx(integral(x/(x^3-x+1), x, 1, 2))
1.45943044687563
sage: A = integral(x/(x^3-x+1), x, 1, 2)
sage:
sage: A_str = str(A)
sage:
sage: eval(preparse("numerical_approx("+A_str +")"))
0.159046901967485
sage:
┌────────────────────────────────────────────────────────────────────┐
│ Sage Version 6.2, Release Date: 2014-05-06 │
│ Type "notebook()" for the browser-based notebook interface. │
│ Type "help()" for help. │
└────────────────────────────────────────────────────────────────────┘
sage: eval(preparse("numerical_approx(integral(x/(x^3-x+1), x, 1, 2))"))
1.64714767119638
sage: numerical_approx(integral(x/(x^3-x+1), x, 1, 2))
1.64714767119638
sage: A = integral(x/(x^3-x+1), x, 1, 2)
sage: A_str = str(A)
sage: eval(preparse("numerical_approx("+A_str +")"))
0.162416510011260
sage:
On the Notebook on the cloud it gives me the following error although the
version is the same as one of the versions I tried locally
version()
'Sage Version 6.5, Release Date: 2015-02-17'
numerical_approx(integral(x/(x^3-x+1), x, 1, 2))
Error in lines 1-1 Traceback (most recent call last): File
"/projects/f700a2f3-7f30-4b47-9f18-e0309eb8c48c/.sagemathcloud/sage_server.py",
line 875, in execute exec compile(block+'\n', '', 'single') in namespace,
locals File "", line 1, in <module> File "<string>", line 1, in <module>
File
"/usr/local/sage/sage-6.5/local/lib/python2.7/site-packages/sage/misc/functional.py",
line 1298, in numerical_approx return x._numerical_approx(prec,
algorithm=algorithm) File "sage/symbolic/expression.pyx", line 4861, in
sage.symbolic.expression.Expression._numerical_approx
(build/cythonized/sage/symbolic/expression.cpp:27184) x =
self._convert(kwds) File "sage/symbolic/expression.pyx", line 1034, in
sage.symbolic.expression.Expression._convert
(build/cythonized/sage/symbolic/expression.cpp:7790) cdef GEx res =
self._gobj.evalf(0, kwds) ValueError: power::eval(): division by zero
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