mod.go

     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  }
    52
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