Source file src/pkg/math/frexp.go

     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.
     4	
     5	package math
     6	
     7	// Frexp breaks f into a normalized fraction
     8	// and an integral power of two.
     9	// It returns frac and exp satisfying f == frac × 2**exp,
    10	// with the absolute value of frac in the interval [½, 1).
    11	//
    12	// Special cases are:
    13	//	Frexp(±0) = ±0, 0
    14	//	Frexp(±Inf) = ±Inf, 0
    15	//	Frexp(NaN) = NaN, 0
    16	func Frexp(f float64) (frac float64, exp int)
    17	
    18	func frexp(f float64) (frac float64, exp int) {
    19		// special cases
    20		switch {
    21		case f == 0:
    22			return f, 0 // correctly return -0
    23		case IsInf(f, 0) || IsNaN(f):
    24			return f, 0
    25		}
    26		f, exp = normalize(f)
    27		x := Float64bits(f)
    28		exp += int((x>>shift)&mask) - bias + 1
    29		x &^= mask << shift
    30		x |= (-1 + bias) << shift
    31		frac = Float64frombits(x)
    32		return
    33	}