NAME ^

examples/pir/circle.pir - Draw a circle on any VT100-compatible screen

SYNOPSIS ^

    % ./parrot examples/pir/circle.pir

DESCRIPTION ^

This draws an ASCII-art representation of a circle (or oval) using only integer arithmetic and no trig.

The algorithm is based on:

  cos(theta+delta) =
            cos(theta) -
            [alpha*cos(theta) + beta*sin(theta)]

and

  sin(theta+delta) =
            sin(theta) -
            [alpha*sin(theta) - beta*cos(theta)]

where

  alpha = 2*sin^2(delta/2) and beta = sin(delta)

(See Numerical Recipes in C / The Art of Scientific Computing)

In this program the value of delta is chosen to be 1/(1<<n) such that it is small enough that

AUTHOR ^

Written for parrot by Nick Glencross <nick.glencross@gmail.com>. Adapted from a machine code program that I wrote for a BBC micro.

COPYRIGHT ^

Same as parrot.


 parrot