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diff --git a/reference/C/CONTRIB/SNIP/combin.c b/reference/C/CONTRIB/SNIP/combin.c
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+/*
+** Compute C(n,m) = the number of combinations of n items,
+** taken m at a time.
+**
+** Written by Thad Smith III, Boulder County, CO.
+** Released to the Public Domain  10/14/91.
+**
+** The def of this function is
+**      C(n,m)  = n! / (m! * (n-m)!).
+** Computing this formula can cause overflow for large values of n,
+** even when C(n,m) would be defined.
+**
+** The first version will not overflow if C(n,m) * (n-m+1) < ULONG_MAX.
+** The second version will not overflow if C(n,m) < ULONG_MAX, but
+** is slightly more complex.
+** Function domain: n >= 0,  0 <= m <= n.
+**
+** Both versions work by reducing the product as it is computed.  It
+** relies on the property that the product on n consecutive integers
+** must be evenly divisible by n.
+**
+** The first version can be changed to make cnm and the return value
+** double to extend the range of the function.
+*/
+
+unsigned long ncomb1 (int n, int m)
+{
+      unsigned long cnm = 1UL;
+      int i;
+
+      if (m*2 >n) m = n-m;
+      for (i=1 ; i <= m; n--, i++)
+            cnm = cnm * n / i;
+      return cnm;
+}
+
+unsigned long ncomb2 (int n, int m)
+{
+      unsigned long cnm = 1UL;
+      int i, f;
+
+      if (m*2 >n) m = n-m;
+      for (i=1 ; i <= m; n--, i++)
+      {
+            if ((f=n) % i == 0)
+                  f   /= i;
+            else  cnm /= i;
+            cnm *= f;
+      }
+      return cnm;
+}
+
+#ifdef TEST
+
+#include <stdio.h>
+#include <stdlib.h>
+
+main (int argc, char *argv[]) {
+    int n,m;
+    n = atoi (argv[1]);
+    m = atoi (argv[2]);
+    printf ("ncomb1 = %lu, ncomb2 = %lu\n", ncomb1(n,m), ncomb2(n,m));
+    return 0;
+}
+
+#endif