1 files changed, 37 insertions, 0 deletions
diff --git a/src/math/log10.go b/src/math/log10.go
new file mode 100644
index 0000000..e6916a5
--- /dev/null
+++ b/src/math/log10.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
+
+// Log10 returns the decimal logarithm of x.
+// The special cases are the same as for Log.
+func Log10(x float64) float64 {
+	if haveArchLog10 {
+		return archLog10(x)
+	}
+	return log10(x)
+}
+
+func log10(x float64) float64 {
+	return Log(x) * (1 / Ln10)
+}
+
+// Log2 returns the binary logarithm of x.
+// The special cases are the same as for Log.
+func Log2(x float64) float64 {
+	if haveArchLog2 {
+		return archLog2(x)
+	}
+	return log2(x)
+}
+
+func log2(x float64) float64 {
+	frac, exp := Frexp(x)
+	// Make sure exact powers of two give an exact answer.
+	// Don't depend on Log(0.5)*(1/Ln2)+exp being exactly exp-1.
+	if frac == 0.5 {
+		return float64(exp - 1)
+	}
+	return Log(frac)*(1/Ln2) + float64(exp)
+}