mirror of
https://github.com/make-42/xyosc
synced 2025-01-19 02:57:34 +01:00
44 lines
871 B
Go
44 lines
871 B
Go
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package math32
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// Ldexp is the inverse of Frexp.
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// It returns frac × 2**exp.
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//
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// Special cases are:
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// Ldexp(±0, exp) = ±0
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// Ldexp(±Inf, exp) = ±Inf
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// Ldexp(NaN, exp) = NaN
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func Ldexp(frac float32, exp int) float32 {
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return ldexp(frac, exp)
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}
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func ldexp(frac float32, exp int) float32 {
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// special cases
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switch {
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case frac == 0:
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return frac // correctly return -0
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case IsInf(frac, 0) || IsNaN(frac):
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return frac
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}
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frac, e := normalize(frac)
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exp += e
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x := Float32bits(frac)
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exp += int(x>>shift)&mask - bias
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if exp < -149 {
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return Copysign(0, frac) // underflow
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}
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if exp > 127 { // overflow
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if frac < 0 {
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return Inf(-1)
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}
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return Inf(1)
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}
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var m float32 = 1
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if exp < -(127 - 1) { // denormal
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exp += shift
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m = 1.0 / (1 << 23) // 1/(2**-23)
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}
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x &^= mask << shift
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x |= uint32(exp+bias) << shift
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return m * Float32frombits(x)
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}
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