RosettaCodeData/Task/Pi/ALGOL-68/pi.alg

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#!/usr/local/bin/a68g --script #
INT base := 10;
MODE YIELDINT = PROC(INT)VOID;
PROC gen pi digits = (INT decimal places, YIELDINT yield)VOID:
BEGIN
INT nine = base - 1;
INT nines := 0, predigit := 0; # First predigit is a 0 #
[decimal places*10 OVER 3]#LONG# INT digits; # We need 3 times the digits to calculate #
FOR place FROM LWB digits TO UPB digits DO digits[place] := 2 OD; # Start with 2s #
FOR place TO decimal places + 1 DO
INT digit := 0;
FOR i FROM UPB digits BY -1 TO LWB digits DO # Work backwards #
INT x := #SHORTEN#(base*digits[i] + #LENG# digit*i);
digits[i] := x MOD (2*i-1);
digit := x OVER (2*i-1)
OD;
digits[LWB digits] := digit MOD base; digit OVERAB base;
nines :=
IF digit = nine THEN
nines + 1
ELSE
IF digit = base THEN
yield(predigit+1); predigit := 0 ;
FOR repeats TO nines DO yield(0) OD # zeros #
ELSE
IF place NE 1 THEN yield(predigit) FI; predigit := digit;
FOR repeats TO nines DO yield(nine) OD
FI;
0
FI
OD;
yield(predigit)
END;
main:(
INT feynman point = 762; # feynman point + 4 is a good test case #
# the 33rd decimal place is a shorter tricky test case #
INT test decimal places = UPB "3.1415926.......................502"-2;
INT width = ENTIER log(base*(1+small real*10));
# iterate throught the digits as they are being found #
# FOR INT digit IN # gen pi digits(test decimal places#) DO ( #,
## (INT digit)VOID: (
printf(($n(width)d$,digit))
)
# OD #);
print(new line)
)