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First Forward Into Logo
Previous: FF5

 

In FF4 you investigated the instruction:

REPEAT 360 [FD 1 RT 1]

Hopefully you altered it as you saw fit and produced some exciting shapes. So it is timely to introduce you to the idea of a variable . As the word implies, a variable is something that varies, something that changes.

You may find the following a quicker way of drawing circles and circular patterns. It is called a procedure and has to be written in a particular way.

TO CIRCLE :CH
REPEAT 360 [ FD :CH RT 1]
END

Notice how the procedure is set out:
First a title / a command TO CIRCLE
then the variable :CH
followed by the instructions REPEAT 360 [ FD :CH RT 1]
then a formal closing of the procedure END

N.B. the variable, :CH could have been any letter or letters that you wish!

 


Now experiment with the procedure:

CIRCLE 3
CIRCLE 6
CIRCLE -3
CIRCLE 9
circles

Building on this idea of a procedure we could have written:

TO CIRC :CH :ANG
REPEAT 360 [ FD :CH RT :ANG]
END

This is a procedure with two variables!

Can you anticipate what will change and what will happen now?
Can you see what is now possible?
Go on experiment! Try:
CIRC 3 3
CIRC 3 6
CIRC 3 30

What is happening?

Why not be bolder and try say:
CIRC 30 90
CIRC 30 45
CIRC 30 18 etc., etc.,
polygons

What do you notice?
What conclusions can you come to?
 

 

Next: FF7