| // 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) |
| } |