Re: LOGO-L> Recursion

[KERRB@Magill.UniSA.edu.au]

Bill MacKay wrote:
>  Can someone explain when we would use tail
>recursion or embedded recursion? Perhaps an example may suffice.
>Thanks in advance,

In logo we tend to use recursion a lot because FOR loops and WHILE loops are 
not primitives.
Examples:
1) to make a turtle move forever

to move
fd 1
move
end

that's tail recursion

2) embedded recursion
Drawing fractals is one example. There are some examples and code on my web 
site at http://www.senet.com.au/~kerrb/
Go to the animation, mainly fractals link. For the code look under Yehuda or 
the HowTo article.

For the best explanation of recursion see Brian Harvey's book, 'Computer 
Science Logo Style' (volume 1). He explains recursion in 4 different ways in 
Chapter 5: the combining method, little people method, tracing method and leap 
of faith method. I'd also recommend Chapter 7: Recursive operations, which I 
found difficult but very rewarding.

Other languages don't seem to use recursion as much but instead rely on FOR and 
WHILE loops. In MicroWorlds tail recursion is simulated visually by means of a 
<many times> button.

-- Bill Kerr
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