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// 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
const (
uvnan = 0x7FF8000000000001
uvinf = 0x7FF0000000000000
uvneginf = 0xFFF0000000000000
mask = 0x7FF
shift = 64 - 11 - 1
bias = 1023
)
// Inf returns positive infinity if sign >= 0, negative infinity if sign < 0.
func Inf(sign int) float64 {
var v uint64
if sign >= 0 {
v = uvinf
} else {
v = uvneginf
}
return Float64frombits(v)
}
// NaN returns an IEEE 754 ``not-a-number'' value.
func NaN() float64 { return Float64frombits(uvnan) }
// IsNaN reports whether f is an IEEE 754 ``not-a-number'' value.
func IsNaN(f float64) (is bool) {
// IEEE 754 says that only NaNs satisfy f != f.
// To avoid the floating-point hardware, could use:
// x := Float64bits(f);
// return uint32(x>>shift)&mask == mask && x != uvinf && x != uvneginf
return f != f
}
// IsInf reports whether f is an infinity, according to sign.
// If sign > 0, IsInf reports whether f is positive infinity.
// If sign < 0, IsInf reports whether f is negative infinity.
// If sign == 0, IsInf reports whether f is either infinity.
func IsInf(f float64, sign int) bool {
// Test for infinity by comparing against maximum float.
// To avoid the floating-point hardware, could use:
// x := Float64bits(f);
// return sign >= 0 && x == uvinf || sign <= 0 && x == uvneginf;
return sign >= 0 && f > MaxFloat64 || sign <= 0 && f < -MaxFloat64
}
// normalize returns a normal number y and exponent exp
// satisfying x == y × 2**exp. It assumes x is finite and non-zero.
func normalize(x float64) (y float64, exp int) {
const SmallestNormal = 2.2250738585072014e-308 // 2**-1022
if Abs(x) < SmallestNormal {
return x * (1 << 52), -52
}
return x, 0
}
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