Source file src/runtime/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	

View as plain text