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368f8cbc75
- enabled for function declarations (not just function literals) - applied gofmt -w $GOROOT/src (look for instance at src/pkg/debug/elf/elf.go) R=r, rsc CC=go-dev http://go/go-review/1026006
102 lines
2.4 KiB
Go
102 lines
2.4 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package math
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const (
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uvnan = 0x7FF0000000000001;
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uvinf = 0x7FF0000000000000;
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uvneginf = 0xFFF0000000000000;
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mask = 0x7FF;
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shift = 64-11-1;
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bias = 1022;
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)
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// Inf returns positive infinity if sign >= 0, negative infinity if sign < 0.
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func Inf(sign int) float64 {
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var v uint64;
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if sign >= 0 {
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v = uvinf;
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} else {
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v = uvneginf;
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}
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return Float64frombits(v);
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}
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// NaN returns an IEEE 754 ``not-a-number'' value.
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func NaN() float64 { return Float64frombits(uvnan) }
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// IsNaN returns whether f is an IEEE 754 ``not-a-number'' value.
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func IsNaN(f float64) (is bool) {
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x := Float64bits(f);
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return uint32(x>>shift)&mask == mask && x != uvinf && x != uvneginf;
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}
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// IsInf returns whether f is an infinity, according to sign.
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// If sign > 0, IsInf returns whether f is positive infinity.
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// If sign < 0, IsInf returns whether f is negative infinity.
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// If sign == 0, IsInf returns whether f is either infinity.
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func IsInf(f float64, sign int) bool {
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x := Float64bits(f);
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return sign >= 0 && x == uvinf || sign <= 0 && x == uvneginf;
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}
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// Frexp breaks f into a normalized fraction
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// and an integral power of two.
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// It returns frac and exp satisfying f == frac × 2<sup>exp</sup>,
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// with the absolute value of frac in the interval [½, 1).
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func Frexp(f float64) (frac float64, exp int) {
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if f == 0 {
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return;
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}
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x := Float64bits(f);
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exp = int((x>>shift)&mask)-bias;
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x &^= mask<<shift;
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x |= bias<<shift;
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frac = Float64frombits(x);
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return;
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}
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// Ldexp is the inverse of Frexp.
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// It returns frac × 2<sup>exp</sup>.
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func Ldexp(frac float64, exp int) float64 {
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x := Float64bits(frac);
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exp += int(x>>shift)&mask;
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if exp <= 0 {
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return 0; // underflow
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}
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if exp >= mask { // 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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x &^= mask<<shift;
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x |= uint64(exp)<<shift;
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return Float64frombits(x);
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}
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// Modf returns integer and fractional floating-point numbers
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// that sum to f.
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// Integer and frac have the same sign as f.
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func Modf(f float64) (int float64, frac float64) {
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if f < 1 {
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if f < 0 {
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int, frac = Modf(-f);
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return -int, -frac;
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}
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return 0, f;
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}
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x := Float64bits(f);
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e := uint(x>>shift)&mask - bias;
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// Keep the top 11+e bits, the integer part; clear the rest.
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if e < 64-11 {
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x &^= 1<<(64-11-e) - 1;
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}
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int = Float64frombits(x);
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frac = f-int;
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return;
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}
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