1 files changed, 80 insertions, 0 deletions
diff --git a/reference/C/CONTRIB/SNIP/factor.c b/reference/C/CONTRIB/SNIP/factor.c
new file mode 100755
index 0000000..4b35d4a
--- /dev/null
+++ b/reference/C/CONTRIB/SNIP/factor.c
@@ -0,0 +1,80 @@
+/*
+** factor.c -- print prime factorization of a number
+** Ray Gardner -- 1985 -- public domain
+** Modified Feb. 1989 by Thad Smith > public domain
+**
+** This version takes numbers up to the limits of double precision.
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+int prevfact = 0;
+void factor (double);
+void show (double, int);
+
+void main (int argc, char *argv[])
+{
+      while ( --argc )
+            factor(atof(*++argv));
+}
+
+void factor (double n)
+{
+      double d;
+      int k;
+
+      prevfact = 0;
+
+      d = n+1;     /* test for roundoff error */
+      if (n+3 != d+2)
+      {
+            printf("%0.0f is too large to process.\n", n);
+            return;
+      }
+      if (fmod(n,1.) != 0.0)
+      {
+            printf("%f is not an integer.\n",n);
+            return;
+      }
+      printf("%0.0f  ",n);
+      if ( n < 2. )
+      {
+            printf("is less than 2.\n");
+            return;
+      }
+      else if ( n > 2. )
+      {
+            d = 2;
+            for ( k = 0; fmod(n,d) == 0.0; k++ )
+                  n /= d;
+            if ( k )
+                  show(d,k);
+            for ( d = 3; d * d <= n; d += 2 )
+            {
+                  for ( k = 0; fmod(n,d) == 0.0; k++ )
+                        n /= d;
+                  if ( k )
+                        show(d,k);
+            }
+      }
+      if ( n > 1 )
+      {
+            if ( ! prevfact )
+                  printf(" is prime");
+            else  show(n,1);
+      }
+      printf("\n");
+}
+
+void show (double d, int k)
+{
+      if ( prevfact )
+            printf(" * ");
+      else  printf(" = ");
+      prevfact++;
+      printf("%0.0f",d);
+      if ( k > 1 )
+            printf("^%d",k);
+}