Add test for mpz module

Demo/scripts/README

@@ -31,6 +31,7 @@ lpwatch.py		Watch BSD line printer queues
 markov.py		Markov chain simulation of words or characters
 methfix.py		Fix old method syntax def f(self, (a1, ..., aN)):
 mkreal.py		Turn a symbolic link into a real file or directory
+mpzpi.py		test mpz -- print digits of pi (compare pi.py)
 objgraph.py		Print object graph from nm output on a library
 pathfix.py		Change #!/usr/local/bin/python into something else
 pdeps.py		Print dependencies between Python modules

Demo/scripts/mpzpi.py

@@ -0,0 +1,34 @@
+#! /usr/local/bin/python
+# Print digits of pi forever.
+#
+# The algorithm, using Python's 'long' integers ("bignums"), works
+# with continued fractions, and was conceived by Lambert Meertens.
+#
+# See also the ABC Programmer's Handbook, by Geurts, Meertens & Pemberton,
+# published by Prentice-Hall (UK) Ltd., 1990.
+
+import sys
+from mpz import mpz
+
+def main():
+	mpzone, mpztwo, mpzten = mpz(1), mpz(2), mpz(10)
+	k, a, b, a1, b1 = mpz(2), mpz(4), mpz(1), mpz(12), mpz(4)
+	while 1:
+		# Next approximation
+		p, q, k = k*k, mpztwo*k+mpzone, k+mpzone
+		a, b, a1, b1 = a1, b1, p*a+q*a1, p*b+q*b1
+		# Print common digits
+		d, d1 = a/b, a1/b1
+		while d == d1:
+			output(d)
+			a, a1 = mpzten*(a%b), mpzten*(a1%b1)
+			d, d1 = a/b, a1/b1
+
+def output(d):
+	# Use write() to avoid spaces between the digits
+	# Use int(d) to avoid a trailing L after each digit
+	sys.stdout.write(`int(d)`)
+	# Flush so the output is seen immediately
+	sys.stdout.flush()
+
+main()