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  //
    17  //	Mod(±Inf, y) = NaN
    18  //	Mod(NaN, y) = NaN
    19  //	Mod(x, 0) = NaN
    20  //	Mod(x, ±Inf) = x
    21  //	Mod(x, NaN) = NaN
    22  func Mod(x, y float64) float64 {
    23  	if haveArchMod {
    24  		return archMod(x, y)
    25  	}
    26  	return mod(x, y)
    27  }
    28  
    29  func mod(x, y float64) float64 {
    30  	if y == 0 || IsInf(x, 0) || IsNaN(x) || IsNaN(y) {
    31  		return NaN()
    32  	}
    33  	y = Abs(y)
    34  
    35  	yfr, yexp := Frexp(y)
    36  	r := x
    37  	if x < 0 {
    38  		r = -x
    39  	}
    40  
    41  	for r >= y {
    42  		rfr, rexp := Frexp(r)
    43  		if rfr < yfr {
    44  			rexp = rexp - 1
    45  		}
    46  		r = r - Ldexp(y, rexp-yexp)
    47  	}
    48  	if x < 0 {
    49  		r = -r
    50  	}
    51  	return r
    52  }
    53
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