1 files changed, 41 insertions, 0 deletions
diff --git a/libgo/go/math/hypot.go b/libgo/go/math/hypot.go
new file mode 100644
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+++ b/libgo/go/math/hypot.go
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+// 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
+
+/*
+	Hypot -- sqrt(p*p + q*q), but overflows only if the result does.
+*/
+
+// Hypot computes Sqrt(p*p + q*q), taking care to avoid
+// unnecessary overflow and underflow.
+//
+// Special cases are:
+//	Hypot(p, q) = +Inf if p or q is infinite
+//	Hypot(p, q) = NaN if p or q is NaN
+func Hypot(p, q float64) float64 {
+	// TODO(rsc): Remove manual inlining of IsNaN, IsInf
+	// when compiler does it for us
+	// special cases
+	switch {
+	case p < -MaxFloat64 || p > MaxFloat64 || q < -MaxFloat64 || q > MaxFloat64: // IsInf(p, 0) || IsInf(q, 0):
+		return Inf(1)
+	case p != p || q != q: // IsNaN(p) || IsNaN(q):
+		return NaN()
+	}
+	if p < 0 {
+		p = -p
+	}
+	if q < 0 {
+		q = -q
+	}
+	if p < q {
+		p, q = q, p
+	}
+	if p == 0 {
+		return 0
+	}
+	q = q / p
+	return p * Sqrt(1+q*q)
+}