|Syntax||MOVE [#ch,] distance|
The QL supports a simplified means of drawing pictures known as turtle graphics. This was based upon an early educational tool, whereby simple commands could be entered into a computer to drive a small robot turtle which moved around the floor and held a pen. This pen could either be up in which case the turtle would just move around, or down in which case a line would be left by the turtle on the floor as it moved.
When a window is first opened, an invisible turtle appears at the graphics origin (altered with SCALE) facing to the right, with its pen in the up position.
The command MOVE forces the turtle in the specified window (default #1) to move in the current direction by the specified distance.
The actual distance moved on screen depends on the current SCALE applicable to that window. If distance is negative, the turtle will move backwards. MOVE always works from the current graphics cursor position, and after using this command, the current graphics cursor is placed at the turtle’s position on screen. MOVE is affected by the current INK colour, FILL and also OVER, just like any other graphics command.
A simple procedure to draw a shape of a set number of equal length sides:
100 DEFine PROCedure POLYGON (chan, sides, side_length) 110 TURNTO #chan,0: PENDOWN #chan 120 FOR k = 1 TO sides 130 MOVE #chan, side_length 140 TURN #chan, 360 / sides 150 END FOR k 155 PENUP #chan 160 END DEFine
Try for example, POLYGON #2,5,10.
The THOR XVI v6.40 tended to crash when using turtle graphics, especially if a channel number was specified.