blob: 8775cdbae4d213d5eba353aa68301f2b5afa6c37 [file] [log] [blame]
 // Copyright 2009 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package math // 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 //extern ldexp func libc_ldexp(float64, int32) float64 func Ldexp(frac float64, exp int) float64 { if exp > MaxInt32 { exp = MaxInt32 } else if exp < MinInt32 { exp = MinInt32 } r := libc_ldexp(frac, int32(exp)) return r } func ldexp(frac float64, exp int) float64 { // 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 := Float64bits(frac) exp += int(x>>shift)&mask - bias if exp < -1075 { return Copysign(0, frac) // underflow } if exp > 1023 { // overflow if frac < 0 { return Inf(-1) } return Inf(1) } var m float64 = 1 if exp < -1022 { // denormal exp += 53 m = 1.0 / (1 << 53) // 2**-53 } x &^= mask << shift x |= uint64(exp+bias) << shift return m * Float64frombits(x) }