float.go

Documentation: runtime

		 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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