github.com/c12o16h1/go/src@v0.0.0-20200114212001-5a151c0f00ed/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  
    23  func mod(x, y float64) float64 {
    24  	if y == 0 || IsInf(x, 0) || IsNaN(x) || IsNaN(y) {
    25  		return NaN()
    26  	}
    27  	y = Abs(y)
    28  
    29  	yfr, yexp := Frexp(y)
    30  	r := x
    31  	if x < 0 {
    32  		r = -x
    33  	}
    34  
    35  	for r >= y {
    36  		rfr, rexp := Frexp(r)
    37  		if rfr < yfr {
    38  			rexp = rexp - 1
    39  		}
    40  		r = r - Ldexp(y, rexp-yexp)
    41  	}
    42  	if x < 0 {
    43  		r = -r
    44  	}
    45  	return r
    46  }