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+/* DISTRIB.C - Procedures for handling distributions over numbers. */
+
+/* Copyright (c) 1995-2012 by Radford M. Neal and Peter Junteng Liu.
+ *
+ * Permission is granted for anyone to copy, use, modify, and distribute
+ * these programs and accompanying documents for any purpose, provided
+ * this copyright notice is retained and prominently displayed, and note
+ * is made of any changes made to these programs.  These programs and
+ * documents are distributed without any warranty, express or implied.
+ * As the programs were written for research purposes only, they have not
+ * been tested to the degree that would be advisable in any important
+ * application.  All use of these programs is entirely at the user's own
+ * risk.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <math.h>
+#include <string.h>
+
+#include "alloc.h"
+#include "distrib.h"
+
+
+/* CREATE A DISTRIBUTION AS SPECIFIED IN A STRING.  Space for the distribution
+   is allocated; the string is not freed. 
+
+   The string must consist either of a single positive integer, representing
+   the distribution over just that number, or have a form such as the
+   following:
+
+      5x2/3.5x1/1.5x4
+
+   This specifies a distribution over 3 numbers, 2, 1, and 4, specified by
+   the second number in each pair, with proportions of 0.5, 0.35, and 0.15, 
+   respectively, specified by the first number in each pair.  The actual
+   proportions are found by dividing the first number in each pair by the sum 
+   of these numbers.
+
+   The distrib type represents the distribution list.  It stores a pointer to 
+   an array of distrib_entry elements along with the length of this array.
+   Each distrib_entry contains a (number,proportion) pair.
+*/
+
+distrib *distrib_create
+( char *c		/* String describing distribution over numbers */
+)
+{
+  distrib *d;
+  char *str, *tstr;
+  int i, n, scan_num, size;
+  double prop, sum;
+  char junk;
+
+  /* Check for special case of a single number. */
+
+  if (sscanf(c,"%d%c",&n,&junk)==1 && n>0)
+  { tstr = chk_alloc ( (int)(4.1+log10(n)), sizeof(*tstr));
+    sprintf(tstr,"1x%d",n);
+    d = distrib_create(tstr);
+    free(tstr);
+    return d;
+  }
+
+  /* Initial scan of string for size and proper usage. */
+  
+  str = c;
+  size = 0;
+  sum = 0;
+
+  d = chk_alloc(1, sizeof *d);
+
+  for (;;)
+  { 
+    scan_num = sscanf(str, "%lgx%d%c", &prop, &n, &junk);
+
+    if ((scan_num!=2 && scan_num!=3) || prop<=0 || n<=0)
+    { return 0;
+    }
+    if (scan_num==3 && junk!='/')
+    { return 0;
+    }
+
+    size += 1;
+    sum += prop;
+
+    if (scan_num==2)
+    { break;
+    }
+    else
+    { str = (char*)strchr(str, '/') + 1;
+    }
+  }
+
+  /* Allocate memory for the list and fill it in */
+
+  d->size = size;
+  d->list = chk_alloc (size, sizeof(distrib_entry));
+
+  i = 0;
+  str = c;
+
+  for (;;)
+  { 
+    scan_num = sscanf(str, "%lgx%d%c", &prop, &n, &junk);
+
+    d->list[i].prop = prop/sum;
+    d->list[i].num = n;
+    i += 1;
+
+    if (scan_num==2)
+    { break;
+    }
+    else if (scan_num==3)
+    { str = (char*)strchr(str, '/') + 1;
+    }
+    else
+    { abort();
+    }
+  }
+
+  return d;
+}
+
+
+/* FREE SPACE OCCUPIED A DISTRIBUTION LIST. */
+
+void distrib_free
+( distrib *d 	/* List to free */
+)
+{ free(d->list);
+  free(d);
+}
+
+
+/* RETURN THE MAXIMUM NUMBER IN A DISTRIBUTION LIST.  Returns 0 if the list 
+   pointer is 0. */
+
+int distrib_max 
+( distrib *d	/* List to examine */
+)
+{ 
+  int i;
+  int cur;
+
+  if (d==0) return 0;
+
+  cur = 0;
+
+  for (i = 1; i<d->size; i++)
+  { if (d->list[i].num > d->list[cur].num)
+    { cur = i;
+    }
+  }
+
+  return d->list[cur].num;
+}
+
+
+/* TEST PROGRAM. */
+
+#ifdef TEST_DISTRIB
+
+main
+( int argc,
+  char **argv
+)
+{
+  distrib *d;
+  int i, j;
+
+  for (i = 1; i<argc; i++)
+  { d = distrib_create(argv[i]);
+    if (d==0)
+    { printf("Error\n\n");
+    }
+    else
+    { for (j = 0; j<distrib_size(d); j++)
+      { printf("%.3f %d\n",distrib_prop(d,j),distrib_num(d,j));
+      }
+      printf("\n");
+    }
+  }
+
+  exit(0);
+}
+
+#endif