1 files changed, 59 insertions, 0 deletions
diff --git a/src/math/bits.go b/src/math/bits.go
new file mode 100644
index 000000000..d85ee9cb1
--- /dev/null
+++ b/src/math/bits.go
@@ -0,0 +1,59 @@
+// 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
+	mask     = 0x7FF
+	shift    = 64 - 11 - 1
+	bias     = 1023
+)
+
+// 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
+}