github.com/riscv/riscv-go@v0.0.0-20200123204226-124ebd6fcc8e/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  
    23  func mod(x, y float64) float64 {
    24  	if y == 0 || IsInf(x, 0) || IsNaN(x) || IsNaN(y) {
    25  		return NaN()
    26  	}
    27  	if y < 0 {
    28  		y = -y
    29  	}
    30  
    31  	yfr, yexp := Frexp(y)
    32  	sign := false
    33  	r := x
    34  	if x < 0 {
    35  		r = -x
    36  		sign = true
    37  	}
    38  
    39  	for r >= y {
    40  		rfr, rexp := Frexp(r)
    41  		if rfr < yfr {
    42  			rexp = rexp - 1
    43  		}
    44  		r = r - Ldexp(y, rexp-yexp)
    45  	}
    46  	if sign {
    47  		r = -r
    48  	}
    49  	return r
    50  }