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-rw-r--r--src/math/bits.go62
1 files changed, 62 insertions, 0 deletions
diff --git a/src/math/bits.go b/src/math/bits.go
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+++ b/src/math/bits.go
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+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package math
+
+const (
+ uvnan = 0x7FF8000000000001
+ uvinf = 0x7FF0000000000000
+ uvneginf = 0xFFF0000000000000
+ uvone = 0x3FF0000000000000
+ mask = 0x7FF
+ shift = 64 - 11 - 1
+ bias = 1023
+ signMask = 1 << 63
+ fracMask = 1<<shift - 1
+)
+
+// Inf returns positive infinity if sign >= 0, negative infinity if sign < 0.
+func Inf(sign int) float64 {
+ var v uint64
+ if sign >= 0 {
+ v = uvinf
+ } else {
+ v = uvneginf
+ }
+ return Float64frombits(v)
+}
+
+// NaN returns an IEEE 754 ``not-a-number'' value.
+func NaN() float64 { return Float64frombits(uvnan) }
+
+// IsNaN reports whether f is an IEEE 754 ``not-a-number'' value.
+func IsNaN(f float64) (is bool) {
+ // IEEE 754 says that only NaNs satisfy f != f.
+ // To avoid the floating-point hardware, could use:
+ // x := Float64bits(f);
+ // return uint32(x>>shift)&mask == mask && x != uvinf && x != uvneginf
+ return f != f
+}
+
+// IsInf reports whether f is an infinity, according to sign.
+// If sign > 0, IsInf reports whether f is positive infinity.
+// If sign < 0, IsInf reports whether f is negative infinity.
+// If sign == 0, IsInf reports whether f is either infinity.
+func IsInf(f float64, sign int) bool {
+ // Test for infinity by comparing against maximum float.
+ // To avoid the floating-point hardware, could use:
+ // x := Float64bits(f);
+ // return sign >= 0 && x == uvinf || sign <= 0 && x == uvneginf;
+ return sign >= 0 && f > MaxFloat64 || sign <= 0 && f < -MaxFloat64
+}
+
+// normalize returns a normal number y and exponent exp
+// satisfying x == y × 2**exp. It assumes x is finite and non-zero.
+func normalize(x float64) (y float64, exp int) {
+ const SmallestNormal = 2.2250738585072014e-308 // 2**-1022
+ if Abs(x) < SmallestNormal {
+ return x * (1 << 52), -52
+ }
+ return x, 0
+}