1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
7 // Ldexp is the inverse of Frexp.
8 // It returns frac × 2**exp.
11 // Ldexp(±0, exp) = ±0
12 // Ldexp(±Inf, exp) = ±Inf
13 // Ldexp(NaN, exp) = NaN
16 func libc_ldexp(float64, int) float64
18 func Ldexp(frac
float64, exp
int) float64 {
19 r
:= libc_ldexp(frac
, exp
)
23 func ldexp(frac
float64, exp
int) float64 {
27 return frac
// correctly return -0
28 case IsInf(frac
, 0) ||
IsNaN(frac
):
31 frac
, e
:= normalize(frac
)
33 x
:= Float64bits(frac
)
34 exp
+= int(x
>>shift
)&mask
- bias
36 return Copysign(0, frac
) // underflow
38 if exp
> 1023 { // overflow
45 if exp
< -1022 { // denormal
47 m
= 1.0 / (1 << 52) // 2**-52
50 x |
= uint64(exp
+bias
) << shift
51 return m
* Float64frombits(x
)