float.go

     1  // Copyright 2017 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 runtime
     6  
     7  import "unsafe"
     8  
     9  var inf = float64frombits(0x7FF0000000000000)
    10  
    11  // isNaN reports whether f is an IEEE 754 ``not-a-number'' value.
    12  func isNaN(f float64) (is bool) {
    13  	// IEEE 754 says that only NaNs satisfy f != f.
    14  	return f != f
    15  }
    16  
    17  // isFinite reports whether f is neither NaN nor an infinity.
    18  func isFinite(f float64) bool {
    19  	return !isNaN(f - f)
    20  }
    21  
    22  // isInf reports whether f is an infinity.
    23  func isInf(f float64) bool {
    24  	return !isNaN(f) && !isFinite(f)
    25  }
    26  
    27  // Abs returns the absolute value of x.
    28  //
    29  // Special cases are:
    30  //	Abs(±Inf) = +Inf
    31  //	Abs(NaN) = NaN
    32  func abs(x float64) float64 {
    33  	const sign = 1 << 63
    34  	return float64frombits(float64bits(x) &^ sign)
    35  }
    36  
    37  // copysign returns a value with the magnitude
    38  // of x and the sign of y.
    39  func copysign(x, y float64) float64 {
    40  	const sign = 1 << 63
    41  	return float64frombits(float64bits(x)&^sign | float64bits(y)&sign)
    42  }
    43  
    44  // Float64bits returns the IEEE 754 binary representation of f.
    45  func float64bits(f float64) uint64 {
    46  	return *(*uint64)(unsafe.Pointer(&f))
    47  }
    48  
    49  // Float64frombits returns the floating point number corresponding
    50  // the IEEE 754 binary representation b.
    51  func float64frombits(b uint64) float64 {
    52  	return *(*float64)(unsafe.Pointer(&b))
    53  }
    54
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