// 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 = 1022; ) // 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) { x := Float64bits(f); return uint32(x>>shift)&mask == mask && x != uvinf && x != uvneginf; } // 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 { x := Float64bits(f); return sign >= 0 && x == uvinf || sign <= 0 && x == uvneginf; } // Frexp breaks f into a normalized fraction // and an integral power of two. // It returns frac and exp satisfying f == frac × 2exp, // with the absolute value of frac in the interval [½, 1). func Frexp(f float64) (frac float64, exp int) { if f == 0 { return } x := Float64bits(f); exp = int((x>>shift)&mask) - bias; x &^= mask << shift; x |= bias << shift; frac = Float64frombits(x); return; } // Ldexp is the inverse of Frexp. // It returns frac × 2exp. func Ldexp(frac float64, exp int) float64 { x := Float64bits(frac); exp += int(x>>shift) & mask; if exp <= 0 { return 0 // underflow } if exp >= mask { // overflow if frac < 0 { return Inf(-1) } return Inf(1); } x &^= mask << shift; x |= uint64(exp) << shift; return Float64frombits(x); } // Modf returns integer and fractional floating-point numbers // that sum to f. // Integer and frac have the same sign as f. func Modf(f float64) (int float64, frac float64) { if f < 1 { if f < 0 { int, frac = Modf(-f); return -int, -frac; } return 0, f; } x := Float64bits(f); e := uint(x>>shift)&mask - bias; // Keep the top 11+e bits, the integer part; clear the rest. if e < 64-11 { x &^= 1<<(64-11-e) - 1 } int = Float64frombits(x); frac = f - int; return; }