[issue32171] Inconsistent results for fractional power of -infinity
Tim Peters
report at bugs.python.org
Wed Nov 29 16:45:32 EST 2017
Tim Peters <tim at python.org> added the comment:
As a comment in the referenced patch says, the intent of the patch was to make behavior match the C99 spec. Among other things, C99's annex F (section F.9.4.4 "The pow functions") says:
"""
— pow(−∞, y) returns −0 for y an odd integer < 0.
— pow(−∞, y) returns +0 for y < 0 and not an odd integer.
— pow(−∞, y) returns −∞ for y an odd integer > 0.
— pow(−∞, y) returns +∞ for y > 0 and not an odd integer.
"""
So the case you show is doing what the standard specifies, under the last of those (y=0.5, which is > 0 and not an odd integer).
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nosy: +tim.peters
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