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-rw-r--r--src/math/hypot.go44
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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 returns Sqrt(p*p + q*q), taking care to avoid
+// unnecessary overflow and underflow.
+//
+// Special cases are:
+//
+// Hypot(±Inf, q) = +Inf
+// Hypot(p, ±Inf) = +Inf
+// Hypot(NaN, q) = NaN
+// Hypot(p, NaN) = NaN
+func Hypot(p, q float64) float64 {
+ if haveArchHypot {
+ return archHypot(p, q)
+ }
+ return hypot(p, q)
+}
+
+func hypot(p, q float64) float64 {
+ p, q = Abs(p), Abs(q)
+ // special cases
+ switch {
+ case IsInf(p, 1) || IsInf(q, 1):
+ return Inf(1)
+ case IsNaN(p) || IsNaN(q):
+ return NaN()
+ }
+ if p < q {
+ p, q = q, p
+ }
+ if p == 0 {
+ return 0
+ }
+ q = q / p
+ return p * Sqrt(1+q*q)
+}