Simple graphics language

A simple graphics language for microcontrollers

We start with a very simple reverse polish notation interpreter with a preprocessor stage

Sample code:

360 for 1 forward 1 right next

Registers:

0 X
1 Y
2 Angle
3 Scale
4 Colour
5 Pen up/down
6 Nested If counter
7

Stack diagrams:

( things read from the stack -- things written on the stack )
x - x position
y - y position
n - number
Example:
  ( n n -- n )
  This means that two numbers were read from the stack, then one number was written back.
  For example a simple addition reads two numbers and writes back the result.

Commands:

Define function:
  To < function name > < code > End
 
Absolute commands
  setcolour     ( colour -- )
  readcolour    ( -- colour )
  setpos        ( x y -- )
  readpos       ( -- x y )

Relative commands:
  penup         ( -- )
  pendown       ( -- )
  forward       ( length -- )
  backward      ( length -- )
  left          ( angle -- )
  right         ( angle -- )
 
Loops:
  for           ( n -- )
  next          ( -- )
  do            ( -- )
  again         ( -- )

Conditionals:
  if            ( n -- )
  else
  endif

Data processing:
  +             ( n n -- n )
  -             ( n n -- n )
  >>            ( n -- n ) 
  <<            ( n -- n )
  and           ( n n -- n )
  or            ( n n -- n )
  eor           ( n n -- n )