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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/pow10.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/pow10.go')
-rw-r--r-- | src/math/pow10.go | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/src/math/pow10.go b/src/math/pow10.go new file mode 100644 index 000000000..f5ad28bb4 --- /dev/null +++ b/src/math/pow10.go @@ -0,0 +1,40 @@ +// Copyright 2009 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 + +// This table might overflow 127-bit exponent representations. +// In that case, truncate it after 1.0e38. +var pow10tab [70]float64 + +// Pow10 returns 10**e, the base-10 exponential of e. +// +// Special cases are: +// Pow10(e) = +Inf for e > 309 +// Pow10(e) = 0 for e < -324 +func Pow10(e int) float64 { + if e <= -325 { + return 0 + } else if e > 309 { + return Inf(1) + } + + if e < 0 { + return 1 / Pow10(-e) + } + if e < len(pow10tab) { + return pow10tab[e] + } + m := e / 2 + return Pow10(m) * Pow10(e-m) +} + +func init() { + pow10tab[0] = 1.0e0 + pow10tab[1] = 1.0e1 + for i := 2; i < len(pow10tab); i++ { + m := i / 2 + pow10tab[i] = pow10tab[m] * pow10tab[i-m] + } +} |