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package math32
// Ldexp is the inverse of Frexp.
// It returns frac × 2**exp.
//
// Special cases are:
// Ldexp(±0, exp) = ±0
// Ldexp(±Inf, exp) = ±Inf
// Ldexp(NaN, exp) = NaN
func Ldexp(frac float32, exp int) float32 {
return ldexp(frac, exp)
}
func ldexp(frac float32, exp int) float32 {
// special cases
switch {
case frac == 0:
return frac // correctly return -0
case IsInf(frac, 0) || IsNaN(frac):
return frac
}
frac, e := normalize(frac)
exp += e
x := Float32bits(frac)
exp += int(x>>shift)&mask - bias
if exp < -149 {
return Copysign(0, frac) // underflow
}
if exp > 127 { // overflow
if frac < 0 {
return Inf(-1)
}
return Inf(1)
}
var m float32 = 1
if exp < -(127 - 1) { // denormal
exp += shift
m = 1.0 / (1 << 23) // 1/(2**-23)
}
x &^= mask << shift
x |= uint32(exp+bias) << shift
return m * Float32frombits(x)
}
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