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7e53ef2fae
Add copyright header to doc.go Keep original comment style (e.g. line comments and block comments). Fix doc comments containing multiple line comments. Remove vanity imports from all files except doc.go. Fixes #12. The source code of fixdocs is located at: https://play.golang.org/p/7RtYLzldsO
112 lines
2.6 KiB
Go
112 lines
2.6 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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// Copyright ©2015 The gonum 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 math32
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import (
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"math"
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)
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const (
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unan = 0x7fc00000
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uinf = 0x7f800000
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uneginf = 0xff800000
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mask = 0x7f8 >> 3
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shift = 32 - 8 - 1
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bias = 127
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)
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// Abs returns the absolute value of x.
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//
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// Special cases are:
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// Abs(±Inf) = +Inf
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// Abs(NaN) = NaN
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func Abs(x float32) float32 {
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switch {
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case x < 0:
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return -x
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case x == 0:
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return 0 // return correctly abs(-0)
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}
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return x
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}
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// Copysign returns a value with the magnitude
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// of x and the sign of y.
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func Copysign(x, y float32) float32 {
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const sign = 1 << 31
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return math.Float32frombits(math.Float32bits(x)&^sign | math.Float32bits(y)&sign)
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}
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// Hypot returns Sqrt(p*p + q*q), taking care to avoid
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// unnecessary overflow and underflow.
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//
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// Special cases are:
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// Hypot(±Inf, q) = +Inf
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// Hypot(p, ±Inf) = +Inf
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// Hypot(NaN, q) = NaN
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// Hypot(p, NaN) = NaN
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func Hypot(p, q float32) float32 {
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// special cases
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switch {
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case IsInf(p, 0) || IsInf(q, 0):
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return Inf(1)
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case IsNaN(p) || IsNaN(q):
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return NaN()
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}
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if p < 0 {
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p = -p
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}
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if q < 0 {
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q = -q
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}
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if p < q {
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p, q = q, p
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}
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if p == 0 {
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return 0
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}
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q = q / p
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return p * Sqrt(1+q*q)
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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) float32 {
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var v uint32
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if sign >= 0 {
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v = uinf
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} else {
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v = uneginf
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}
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return math.Float32frombits(v)
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}
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// IsInf reports whether f is an infinity, according to sign.
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// If sign > 0, IsInf reports whether f is positive infinity.
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// If sign < 0, IsInf reports whether f is negative infinity.
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// If sign == 0, IsInf reports whether f is either infinity.
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func IsInf(f float32, sign int) bool {
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// Test for infinity by comparing against maximum float.
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// To avoid the floating-point hardware, could use:
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// x := math.Float32bits(f);
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// return sign >= 0 && x == uinf || sign <= 0 && x == uneginf;
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return sign >= 0 && f > math.MaxFloat32 || sign <= 0 && f < -math.MaxFloat32
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}
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// IsNaN reports whether f is an IEEE 754 ``not-a-number'' value.
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func IsNaN(f float32) (is bool) {
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// IEEE 754 says that only NaNs satisfy f != f.
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// To avoid the floating-point hardware, could use:
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// x := math.Float32bits(f);
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// return uint32(x>>shift)&mask == mask && x != uinf && x != uneginf
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return f != f
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}
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// NaN returns an IEEE 754 ``not-a-number'' value.
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func NaN() float32 { return math.Float32frombits(unan) }
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