1 files changed, 12 insertions, 0 deletions
diff --git a/src/math/copysign.go b/src/math/copysign.go
new file mode 100644
index 0000000..3a30afb
--- /dev/null
+++ b/src/math/copysign.go
@@ -0,0 +1,12 @@
+// Copyright 2010 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
+
+// Copysign returns a value with the magnitude of f
+// and the sign of sign.
+func Copysign(f, sign float64) float64 {
+	const signBit = 1 << 63
+	return Float64frombits(Float64bits(f)&^signBit | Float64bits(sign)&signBit)
+}