1 files changed, 46 insertions, 0 deletions
diff --git a/libslang/examples/prime.sl b/libslang/examples/prime.sl
new file mode 100644
index 0000000..154f2ee
--- /dev/null
+++ b/libslang/examples/prime.sl
@@ -0,0 +1,46 @@
+#! /usr/bin/env slsh
+% This demo counts the number of primes between 2 and some integer
+
+static define usage ()
+{
+   () = fprintf (stderr, "Usage: %S <integer greater than 2>\n", __argv[0]);
+   exit (1);
+}
+
+define count_primes (num)
+{
+   variable size = (num - 1)/2;
+   variable nonprimes = Char_Type[size + 1];   %  last one is sentinel
+   variable count = 1;
+   variable prime = 3;
+   variable i = 0;
+
+   do 
+     {
+        count++;
+	%()=printf ("%S\n", prime);
+
+	nonprimes [[i:size-1:prime]] = 1;
+	variable i_save = i;
+	while (i++, nonprimes[i])
+	  ;
+	prime += 2 * (i - i_save);
+     } 
+   while (i < size);
+   
+   return count;
+}
+
+
+static variable Num;
+
+if (__argc != 2)
+  usage ();
+Num = integer (__argv[1]);
+if (Num < 3)
+  usage ();
+
+tic ();
+()=printf ("\n\n%d primes between 2 and %d in %f seconds.\n",
+	   count_primes (Num), Num, toc ());
+exit(0);