github.com/AESNooper/go/src@v0.0.0-20220218095104-b56a4ab1bbbb/math/modf.go (about)

     1  // Copyright 2009 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  // Modf returns integer and fractional floating-point numbers
     8  // that sum to f. Both values have the same sign as f.
     9  //
    10  // Special cases are:
    11  //	Modf(±Inf) = ±Inf, NaN
    12  //	Modf(NaN) = NaN, NaN
    13  func Modf(f float64) (int float64, frac float64) {
    14  	if haveArchModf {
    15  		return archModf(f)
    16  	}
    17  	return modf(f)
    18  }
    19  
    20  func modf(f float64) (int float64, frac float64) {
    21  	if f < 1 {
    22  		switch {
    23  		case f < 0:
    24  			int, frac = Modf(-f)
    25  			return -int, -frac
    26  		case f == 0:
    27  			return f, f // Return -0, -0 when f == -0
    28  		}
    29  		return 0, f
    30  	}
    31  
    32  	x := Float64bits(f)
    33  	e := uint(x>>shift)&mask - bias
    34  
    35  	// Keep the top 12+e bits, the integer part; clear the rest.
    36  	if e < 64-12 {
    37  		x &^= 1<<(64-12-e) - 1
    38  	}
    39  	int = Float64frombits(x)
    40  	frac = f - int
    41  	return
    42  }