Problem Statement

Create a program to continually calculate and output the next decimal digit of

π

{\displaystyle \pi }

(pi). The program should continue forever (until it is aborted by the user) calculating and outputting each decimal digit in succession. The output should be a decimal sequence beginning   3.14159265 ...

Note: this task is about   calculating   pi.   For information on built-in pi constants see Real constants and functions.

Related Task Arithmetic-geometric mean/Calculate Pi

Let's start with the solution:

: calcPiDigits 
| q r t k n l |
   1 ->q 0 ->r 1 ->t 1 ->k 3 ->n 3 -> l

   while( true ) [
      4 q * r + t - n t * < ifTrue: [
         n print
         r n t * - 10 *
         3 q * r + 10 * t / n 10 * - ->n ->r
         q 10 * ->q
         ]
      else: [
         2 q * r + l * 
         7 k * q * 2 + r l * + t l * / ->n ->r
         k q * ->q
         t l * ->t
         l 2 + ->l
         k 1+  ->k
         ]
       ] ;