blob: 77bcdbe1ce649a662049c005e34c06dfbecd6e86 [file] [log] [blame]
 // 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 uvone = 0x3FF0000000000000 mask = 0x7FF shift = 64 - 11 - 1 bias = 1023 signMask = 1 << 63 fracMask = 1<= 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 }