| // 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 = 0x7FF0000000000001 |
| 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 returns 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 returns whether f is an infinity, according to sign. |
| // If sign > 0, IsInf returns whether f is positive infinity. |
| // If sign < 0, IsInf returns whether f is negative infinity. |
| // If sign == 0, IsInf returns 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 |
| } |