picolisp

commit 7bf79f816239f334e6f4d9554f66371d4c843f19
parent 51e91691f1f61a15bc412986faa0694a6f60f02d
Author: Alexander Burger <abu@software-lab.de>
Date:   Wed,  4 May 2011 18:20:15 +0200

Added unbounded PI digit stream generation
Diffstat:
M
misc/pi.l
 | 
27
++++++++++++++++++++++++++-

1 file changed, 26 insertions(+), 1 deletion(-)
diff --git a/misc/pi.l b/misc/pi.l
@@ -1,4 +1,4 @@
-# 14aug05abu
+# 03may11abu
 # (c) Software Lab. Alexander Burger
 
 ##############################
@@ -21,3 +21,28 @@
 
 (test 3141592653589793238462643383279502884197169399375105820975043
    (pi 60) )
+
+
+###################################
+# Spigot algorithm (Jeremy Gibbons)
+# Print next digit of PI (unbounded)
+
+(de piDigit ()
+   (job '((Q . 1) (R . 0) (S . 1) (K . 1) (N . 3) (L . 3))
+      (while (>= (- (+ R (* 4 Q)) S) (* N S))
+         (mapc set '(Q R S K N L)
+            (list
+               (* Q K)
+               (* L (+ R (* 2 Q)))
+               (* S L)
+               (inc K)
+               (/ (+ (* Q (+ 2 (* 7 K))) (* R L)) (* S L))
+               (+ 2 L) ) ) )
+      (prog1 N
+         (let M (- (/ (* 10 (+ R (* 3 Q))) S) (* 10 N))
+            (setq Q (* 10 Q)  R (* 10 (- R (* N S)))  N M) ) ) ) )
+
+(prin (piDigit) ".")
+(loop
+   (prin (piDigit))
+   (flush) )