From 7249ea4df2b4f12a4e7ed446f270cea87e4ffd34 Mon Sep 17 00:00:00 2001 From: Rob Pike Date: Tue, 9 Jun 2009 09:53:44 -0700 Subject: mv src/lib to src/pkg tests: all.bash passes, gobuild still works, godoc still works. R=rsc OCL=30096 CL=30102 --- src/pkg/math/pow10.go | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) create mode 100644 src/pkg/math/pow10.go (limited to 'src/pkg/math/pow10.go') diff --git a/src/pkg/math/pow10.go b/src/pkg/math/pow10.go new file mode 100644 index 000000000..fcdd6e0a1 --- /dev/null +++ b/src/pkg/math/pow10.go @@ -0,0 +1,37 @@ +// 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. + * it is important to get all one can from this + * routine since it is used in atof to scale numbers. + * the presumption is that GO converts fp numbers better + * than multipication of lower powers of 10. + */ + +var pow10tab [70]float64; + +// Pow10 returns 10**x, the base-10 exponential of x. +func Pow10(e int) float64 { + 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