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author | Russ Cox <rsc@golang.org> | 2014-09-08 00:08:51 -0400 |
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committer | Russ Cox <rsc@golang.org> | 2014-09-08 00:08:51 -0400 |
commit | 8528da672cc093d4dd06732819abc1f7b6b5a46e (patch) | |
tree | 334be80d4a4c85b77db6f6fdb67cbf0528cba5f5 /src/math/remainder.go | |
parent | 73bcb69f272cbf34ddcc9daa56427a8683b5a95d (diff) | |
download | go-8528da672cc093d4dd06732819abc1f7b6b5a46e.tar.gz |
build: move package sources from src/pkg to src
Preparation was in CL 134570043.
This CL contains only the effect of 'hg mv src/pkg/* src'.
For more about the move, see golang.org/s/go14nopkg.
Diffstat (limited to 'src/math/remainder.go')
-rw-r--r-- | src/math/remainder.go | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/src/math/remainder.go b/src/math/remainder.go new file mode 100644 index 000000000..9a4e4154c --- /dev/null +++ b/src/math/remainder.go @@ -0,0 +1,85 @@ +// 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 + +// The original C code and the comment below are from +// FreeBSD's /usr/src/lib/msun/src/e_remainder.c and came +// with this notice. The go code is a simplified version of +// the original C. +// +// ==================================================== +// Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. +// +// Developed at SunPro, a Sun Microsystems, Inc. business. +// Permission to use, copy, modify, and distribute this +// software is freely granted, provided that this notice +// is preserved. +// ==================================================== +// +// __ieee754_remainder(x,y) +// Return : +// returns x REM y = x - [x/y]*y as if in infinite +// precision arithmetic, where [x/y] is the (infinite bit) +// integer nearest x/y (in half way cases, choose the even one). +// Method : +// Based on Mod() returning x - [x/y]chopped * y exactly. + +// Remainder returns the IEEE 754 floating-point remainder of x/y. +// +// Special cases are: +// Remainder(±Inf, y) = NaN +// Remainder(NaN, y) = NaN +// Remainder(x, 0) = NaN +// Remainder(x, ±Inf) = x +// Remainder(x, NaN) = NaN +func Remainder(x, y float64) float64 + +func remainder(x, y float64) float64 { + const ( + Tiny = 4.45014771701440276618e-308 // 0x0020000000000000 + HalfMax = MaxFloat64 / 2 + ) + // special cases + switch { + case IsNaN(x) || IsNaN(y) || IsInf(x, 0) || y == 0: + return NaN() + case IsInf(y, 0): + return x + } + sign := false + if x < 0 { + x = -x + sign = true + } + if y < 0 { + y = -y + } + if x == y { + return 0 + } + if y <= HalfMax { + x = Mod(x, y+y) // now x < 2y + } + if y < Tiny { + if x+x > y { + x -= y + if x+x >= y { + x -= y + } + } + } else { + yHalf := 0.5 * y + if x > yHalf { + x -= y + if x >= yHalf { + x -= y + } + } + } + if sign { + x = -x + } + return x +} |