# HG changeset patch
# User jwe
# Date 745728652 0
# Node ID 46807fe3db5b4c3f61e43acefd7767b1d9d3d50a
# Parent  2876864f1fdb65c29cb4f9fbf8f4240e843041a3
[project @ 1993-08-19 02:50:52 by jwe]
Initial revision

diff -r 2876864f1fdb -r 46807fe3db5b scripts/miscellaneous/list_primes.m
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/miscellaneous/list_primes.m	Thu Aug 19 02:50:52 1993 +0000
@@ -0,0 +1,62 @@
+function retval = list_primes (n)
+
+# usage: list_primes (n)
+#
+# List the first n primes.  If n is unspecified, the first 30 primes
+# are listed.
+#
+# The algorithm used is from page 218 of the TeXbook.
+
+  if (nargin > 0)
+    if (! is_scalar (n))
+      error ("list_primes: argument must be a scalar");
+    endif
+  endif
+
+  if (nargin == 0)
+    n = 30;
+  endif
+
+  if (n == 1)
+    retval = 2;
+    return;
+  endif
+
+  if (n == 2)
+    retval = [2; 3];
+    return;
+  endif
+
+  retval = zeros (1, n);
+  retval (1) = 2;
+  retval (2) = 3;
+
+  n = n - 2;
+  i = 3;
+  p = 5;
+  while (n > 0)
+
+    is_prime = 1;
+    is_unknown = 1;
+    d = 3;
+    while (is_unknown)
+      a = fix (p / d);
+      if (a <= d)
+        is_unknown = 0;
+      endif
+      if (a * d == p)
+        is_prime = 0;
+        is_unknown = 0;
+      endif
+      d = d + 2;
+    endwhile
+
+    if (is_prime)
+      retval (i++) = p;
+      n--;
+    endif
+    p = p + 2;
+
+  endwhile
+
+endfunction
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