1 files changed, 47 insertions, 0 deletions
diff --git a/src/math/nextafter.go b/src/math/nextafter.go
new file mode 100644
index 000000000..bbb139986
--- /dev/null
+++ b/src/math/nextafter.go
@@ -0,0 +1,47 @@
+// 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
+
+// Nextafter32 returns the next representable float32 value after x towards y.
+// Special cases:
+//	Nextafter32(x, x)   = x
+//      Nextafter32(NaN, y) = NaN
+//      Nextafter32(x, NaN) = NaN
+func Nextafter32(x, y float32) (r float32) {
+	switch {
+	case IsNaN(float64(x)) || IsNaN(float64(y)): // special case
+		r = float32(NaN())
+	case x == y:
+		r = x
+	case x == 0:
+		r = float32(Copysign(float64(Float32frombits(1)), float64(y)))
+	case (y > x) == (x > 0):
+		r = Float32frombits(Float32bits(x) + 1)
+	default:
+		r = Float32frombits(Float32bits(x) - 1)
+	}
+	return
+}
+
+// Nextafter returns the next representable float64 value after x towards y.
+// Special cases:
+//	Nextafter64(x, x)   = x
+//      Nextafter64(NaN, y) = NaN
+//      Nextafter64(x, NaN) = NaN
+func Nextafter(x, y float64) (r float64) {
+	switch {
+	case 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
+}