github.com/code-reading/golang@v0.0.0-20220303082512-ba5bc0e589a3/go/src/math/mod.go (about) 1 // Copyright 2009-2010 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package math 6 7 /* 8 Floating-point mod function. 9 */ 10 11 // Mod returns the floating-point remainder of x/y. 12 // The magnitude of the result is less than y and its 13 // sign agrees with that of x. 14 // 15 // Special cases are: 16 // Mod(±Inf, y) = NaN 17 // Mod(NaN, y) = NaN 18 // Mod(x, 0) = NaN 19 // Mod(x, ±Inf) = x 20 // Mod(x, NaN) = NaN 21 func Mod(x, y float64) float64 { 22 if haveArchMod { 23 return archMod(x, y) 24 } 25 return mod(x, y) 26 } 27 28 func mod(x, y float64) float64 { 29 if y == 0 || IsInf(x, 0) || IsNaN(x) || IsNaN(y) { 30 return NaN() 31 } 32 y = Abs(y) 33 34 yfr, yexp := Frexp(y) 35 r := x 36 if x < 0 { 37 r = -x 38 } 39 40 for r >= y { 41 rfr, rexp := Frexp(r) 42 if rfr < yfr { 43 rexp = rexp - 1 44 } 45 r = r - Ldexp(y, rexp-yexp) 46 } 47 if x < 0 { 48 r = -r 49 } 50 return r 51 }