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Fix #17017 (math edge cases) (#17588)

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* Fix #17017

Add more test cases

* USe signbit in example
This commit is contained in:
konsumlamm 2021-04-01 12:47:56 +02:00 • committed by GitHub
commit f0587e02e2
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2 changed files with 51 additions and 12 deletions
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18
lib/pure/math.nim
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@ -949,18 +949,25 @@ func frexp*[T: float32|float64](x: T): tuple[frac: T, exp: int] {.inline.} =
doAssert frexp(8.0) == (0.5, 4)
doAssert frexp(-8.0) == (-0.5, 4)
doAssert frexp(0.0) == (0.0, 0)
# special cases:
when not defined(windows):
doAssert frexp(-0.0) == (-0.0, 0) # signbit preserved for +-0
doAssert frexp(Inf).frac == Inf # +- Inf preserved
doAssert frexp(NaN).frac.isNaN
doAssert frexp(-0.0).frac.signbit # signbit preserved for +-0
doAssert frexp(Inf).frac == Inf # +- Inf preserved
doAssert frexp(NaN).frac.isNaN
when not defined(js):
var exp: cint
result.frac = c_frexp2(x, exp)
result.exp = exp
else:
if x == 0.0:
result = (0.0, 0)
# reuse signbit implementation
let uintBuffer = toBitsImpl(x)
if (uintBuffer[1] shr 31) != 0:
# x is -0.0
result = (-0.0, 0)
else:
result = (0.0, 0)
elif x < 0.0:
result = frexp(-x)
result.frac = -result.frac
@ -980,6 +987,7 @@ func frexp*[T: float32|float64](x: T, exponent: var int): T {.inline.} =
var x: int
doAssert frexp(5.0, x) == 0.625
doAssert x == 3
(result, exponent) = frexp(x)