1 files changed, 86 insertions, 0 deletions
diff --git a/gsl-1.9/histogram/find.c b/gsl-1.9/histogram/find.c
new file mode 100644
index 0000000..b252a36
--- /dev/null
+++ b/gsl-1.9/histogram/find.c
@@ -0,0 +1,86 @@
+/* histogram/find.c
+ * 
+ * Copyright (C) 1996, 1997, 1998, 1999, 2000 Brian Gough
+ * 
+ * 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 2 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, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+/* determines whether to optimize for linear ranges  */
+#define LINEAR_OPT 1
+
+static int find (const size_t n, const double range[], 
+                 const double x, size_t * i);
+
+static int
+find (const size_t n, const double range[], const double x, size_t * i)
+{
+  size_t i_linear, lower, upper, mid;
+
+  if (x < range[0])
+    {
+      return -1;
+    }
+
+  if (x >= range[n])
+    {
+      return +1;
+    }
+
+  /* optimize for linear case */
+
+#ifdef LINEAR_OPT
+  {
+    double u =  (x - range[0]) / (range[n] - range[0]);
+    i_linear = (size_t) (u * n);
+  }
+
+  if (x >= range[i_linear] && x < range[i_linear + 1])
+    {
+      *i = i_linear;
+      return 0;
+    }
+#endif
+
+  /* perform binary search */
+
+  upper = n ;
+  lower = 0 ;
+
+  while (upper - lower > 1)
+    {
+      mid = (upper + lower) / 2 ;
+      
+      if (x >= range[mid])
+        {
+          lower = mid ;
+        }
+      else
+        {
+          upper = mid ;
+        }
+    }
+
+  *i = lower ;
+
+  /* sanity check the result */
+
+  if (x < range[lower] || x >= range[lower + 1])
+    {
+      GSL_ERROR ("x not found in range", GSL_ESANITY);
+    }
+
+  return 0;
+}
+