First Forward into Logo 10: Count Up - Count Down

What happens when a procedure calls itself?

Age

11 to 18

Challenge level

Exploring and noticing Working systematically Conjecturing and generalising Visualising and representing Reasoning, convincing and proving

Being curious Being resourceful Being resilient Being collaborative

Problem

WARNING - You may need to press "Halt" to stop some of these procedures!!

You might like to begin by thinking about two procedures:

TO COUNTUP :X
 
PR :X
 
COUNTUP :X + 3
 
END

Try COUNTUP 2

TO COUNTDOWN :X
 
PR :X
 
COUNTDOWN :X - 2
 
END

Try COUNTDOWN 189

As before, discuss with others and try evaluating the procedures BEFORE copying them out and experimenting further.

Now, here are two more procedures you might like to think about:

TO FAC :X :A
 
PR :A 
 
FAC :X + 1 :X * :A
 
END

Try FAC 11

TO MULTI :X :A
 
PR :A
 
MULTI :X :X + :A
 
END

Try MULTI 2 0; MULTI 2 1 ...etc

Can all the sequences of number that you know, be programmed in LOGO?

Why not submit other procedures that you have used to generate other special number sequences?

While geometrically

...the challenge is to program ELEGANTLY the drawing of the smaller pentagrams onto the 'arms' of the larger one, as shown below.

Next: FF11