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lilydjwg opened this issue Jul 7, 2020 · 2 comments · Fixed by #2030
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(-2) ** 0.5 yields NaN #1986

lilydjwg opened this issue Jul 7, 2020 · 2 comments · Fixed by #2030
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C-compat A discrepancy between RustPython and CPython

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@lilydjwg
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lilydjwg commented Jul 7, 2020

Feature

non-integer power of negative numbers.

Python Documentation
@lilydjwg lilydjwg added the C-compat A discrepancy between RustPython and CPython label Jul 7, 2020
@youknowone
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CPython:

>>> float.__rpow__(0.5, -2)
(8.659560562354934e-17+1.4142135623730951j)

RustPython:

>>>>> float.__rpow__(0.5, -2)
NaN

@minoring
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I am handling this issue :)

minoring added a commit to minoring/RustPython that referenced this issue Jul 27, 2020
@minoring
Fix RustPython#1986 which (-2) ** 0.5 yields NaN.
0827b84 
Result:

RustPython gives
`float.__rpow__(0.5, -2)
(0.00000000000000008659560562354934+1.4142135623730951j)`

CPython 3.85 gives
`>>> float.__rpow__(0.5, -2)
(8.659560562354934e-17+1.4142135623730951j)`
@minoring minoring mentioned this issue Jul 27, 2020
Merged
minoring added a commit to minoring/RustPython that referenced this issue Jul 27, 2020
@minoring
Fix RustPython#1986 which (-2) ** 0.5 yields NaN.
6244a50 
Result:

RustPython gives
`float.__rpow__(0.5, -2)
(0.00000000000000008659560562354934+1.4142135623730951j)`

CPython 3.85 gives
`>>> float.__rpow__(0.5, -2)
(8.659560562354934e-17+1.4142135623730951j)`
minoring added a commit to minoring/RustPython that referenced this issue Jul 27, 2020
@minoring
Fix RustPython#1986 which (-2) ** 0.5 yields NaN.
a57c43b 
Result:

RustPython gives
`float.__rpow__(0.5, -2)
(0.00000000000000008659560562354934+1.4142135623730951j)`

CPython 3.85 gives
`>>> float.__rpow__(0.5, -2)
(8.659560562354934e-17+1.4142135623730951j)`
minoring added a commit to minoring/RustPython that referenced this issue Jul 28, 2020
@minoring
Fix RustPython#1986 which (-2) ** 0.5 yields NaN.
ee8a66a 
Result:

RustPython gives
`float.__rpow__(0.5, -2)
(0.00000000000000008659560562354934+1.4142135623730951j)`

CPython 3.85 gives
`>>> float.__rpow__(0.5, -2)
(8.659560562354934e-17+1.4142135623730951j)`
youknowone pushed a commit that referenced this issue Jul 29, 2020
@minoring
Fix negative ** fraction to returns complex value
6032b54 
Fix #1986 which (-2) ** 0.5 yields NaN.

Result:

RustPython gives
`float.__rpow__(0.5, -2)
(0.00000000000000008659560562354934+1.4142135623730951j)`

CPython 3.85 gives
`>>> float.__rpow__(0.5, -2)
(8.659560562354934e-17+1.4142135623730951j)`
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Fix #1986 which (-2) ** 0.5 yields NaN. minoring/RustPython
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@youknowone @lilydjwg @minoring