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author | Tianon Gravi <admwiggin@gmail.com> | 2015-01-15 12:50:40 -0700 |
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committer | Tianon Gravi <admwiggin@gmail.com> | 2015-01-15 12:50:40 -0700 |
commit | 2a0db60599fdd75b1bc3e297180fbe1282763759 (patch) | |
tree | 68d43c3e30d9ab961ddf6b7365201ca6b675b253 /src/math/pow10.go | |
parent | ef33cba3c8de6c431df56503df51fcd3a473c89e (diff) | |
parent | f154da9e12608589e8d5f0508f908a0c3e88a1bb (diff) | |
download | golang-2a0db60599fdd75b1bc3e297180fbe1282763759.tar.gz |
Merge tag 'upstream/1.4' into debian-experimental
* tag 'upstream/1.4':
Imported Upstream version 1.4
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] + } +} |