Status: Valid
Owner: ----
Labels: Type-Defect Priority-Medium Evalf
New issue 4093 by [email protected]: log(x).evalf(subs={x: 0}) gives
TypeError: 'NoneType' object is not iterable
http://code.google.com/p/sympy/issues/detail?id=4093
In [14]: log(x).evalf(subs={x: 0})
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-14-cffc23219cc7> in <module>()
----> 1 log(x).evalf(subs={x: 0})
/Users/aaronmeurer/Documents/Python/sympy/sympy/sympy/core/evalf.py in
evalf(self, n, subs, maxn, chop, strict, quad, verbose)
1280 options['quad'] = quad
1281 try:
-> 1282 result = evalf(self, prec + 4, options)
1283 except NotImplementedError:
1284 # Fall back to the ordinary evalf
/Users/aaronmeurer/Documents/Python/sympy/sympy/sympy/core/evalf.py in
evalf(x, prec, options)
1180 try:
1181 rf = evalf_table[x.func]
-> 1182 r = rf(x, prec, options)
1183 except KeyError:
1184 try:
/Users/aaronmeurer/Documents/Python/sympy/sympy/sympy/core/evalf.py in
evalf_log(expr, prec, options)
775 return re[0], im, re[2], prec
776
--> 777 imaginary_term = (mpf_cmp(xre, fzero) < 0)
778
779 re = mpf_log(mpf_abs(xre), prec, rnd)
/Users/aaronmeurer/Documents/Python/sympy/sympy/sympy/mpmath/libmp/libmpf.py
in
mpf_cmp(s, t)
553 # A full subtraction is relatively slow, however, so we first
try to
554 # look at the components.
--> 555 ssign, sman, sexp, sbc = s
556 tsign, tman, texp, tbc = t
557
TypeError: 'NoneType' object is not iterable
The reason is that log(0) is not defined, but it should probably raise a
better error, like ValueError, or return nan or something (log(0) directly
returns zoo, so maybe nan wouldn't be correct, I don't know).
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