1 files changed, 29 insertions, 0 deletions
diff --git a/libgo/go/math/nextafter.go b/libgo/go/math/nextafter.go
new file mode 100644
index 000000000..86114340c
--- /dev/null
+++ b/libgo/go/math/nextafter.go
@@ -0,0 +1,29 @@
+// 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
+
+// Nextafter returns the next representable value after x towards y.
+// If x == y, then x is returned.
+//
+// Special cases are:
+//	Nextafter(NaN, y) = NaN
+//	Nextafter(x, NaN) = NaN
+func Nextafter(x, y float64) (r float64) {
+	// TODO(rsc): Remove manual inlining of IsNaN
+	// when compiler does it for us
+	switch {
+	case x != x || y != y: // IsNaN(x) || IsNaN(y): // special case
+		r = NaN()
+	case x == y:
+		r = x
+	case x == 0:
+		r = Copysign(Float64frombits(1), y)
+	case (y > x) == (x > 0):
+		r = Float64frombits(Float64bits(x) + 1)
+	default:
+		r = Float64frombits(Float64bits(x) - 1)
+	}
+	return r
+}