Block 2130
( init-4.th - pi series )
VARIABLE PI-ACC
VARIABLE PI-SGN
1000000 CONSTANT PI-SCALE
: RESET-PI 0 PI-ACC ! 1 PI-SGN ! ;
: FLIP-SIGN
  PI-SGN @ 0< IF 1 PI-SGN ! ELSE -1 PI-SGN ! THEN
;
Block 2131
: PI-STEP ( n -- )
  2 * 1 +
  PI-SCALE SWAP / PI-SGN @ * PI-ACC @ + PI-ACC !
  FLIP-SIGN
;
: PI-CHUNK
  100 0 DO
    I PI-STEP
  LOOP
;
Block 2132
: DO-PI
  RESET-PI
  5 0 DO
    PI-CHUNK
  LOOP
;
: RUN-PI
  8 0 DO
    DO-PI
  LOOP
;
RUN-PI
." 4:dopi-ok" CR