New module 'log10l'.

[gnulib.git] / lib / log10l.c

diff --git a/lib/log10l.c b/lib/log10l.c
new file mode 100644 (file)
index 0000000..ecaacb2
--- /dev/null
+++ b/lib/log10l.c
@@ -0,0 +1,42 @@
+/* Base 10 logarithmic function.
+   Copyright (C) 2012 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+/* Specification.  */
+#include <math.h>
+
+#if HAVE_SAME_LONG_DOUBLE_AS_DOUBLE
+
+long double
+log10l (long double x)
+{
+  return log10 (x);
+}
+
+#else
+
+/* 1 / log(10) */
+static const long double inv_log10 =
+  0.43429448190325182765112891891660508229439700580366656611445378316586464920887L;
+
+long double
+log10l (long double x)
+{
+  return logl (x) * inv_log10;
+}
+
+#endif