Oops, sorry! Yesterday evening I noticed that I messed it up, but was too tired to dig into it.
On Wed, Feb 12, 2025 at 02:28:25PM -0800, Lindsay Lawrence wrote: > Question: Without fully understanding the algorithm, it seems N is the next > digit to return... Right. I posted the original 'while' version many years ago in Rosetta Code: https://rosettacode.org/wiki/Pi#PicoLisp I translated it from the Haskell version, also without fully understanding the algorithm :) > But why write that as (swap 'N M)? M is NIL if not defined but otherwise > may have some other random value which, if set, does cause results to go > astray. Exactly! I noticed yesterday that 'lint' complained about the 'M'. When I built the tco version yesterday, I experimended with both versions, and somehow the 'M' code was lost :( But very very strange that it seems to output the correct digits as long as 'M' is NIL! This is the correct original version: (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) ) ) ) ) and this the tco version: (de piDigit () (job '((Q . 1) (R . 0) (S . 1) (K . 1) (N . 3) (L . 3)) (tco (Q R S K N L) (if (>= (- (+ R (* 4 Q)) S) (* N S)) (tc (* 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) ) ) ) ) ) Sorry again for the confusion! ☺/ A!ex -- UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
