Re: LOGO-L> STOP and STOPME

[KERRB@Magill.UniSA.edu.au]

Yehuda wrote:-
>Playing music is done apparently by a seperate processor. But I still>
>can't see how MW can process two programs (except music) paralelly.

the music is just one example.
MW can launch different turtles and procedures independently, using the MW 
launch primitive
Hopefully, someone else can provide the technical details but to be sure 
parallel processing is a major improvement over earlier versions of logo IMHO. 
It was much more difficult to teach kids how to do multiple animations using 
earlier version such as LogoWriter, where you had to talk to one turtle, ask it 
move a bit, then talk to the other one, ask it to move a bit, then put a repeat 
outside of the whole thing.
> 
>> >Do you think that in MW, STOPME is an essential command and normally one
>> >can't do without it?
> 
>> Here is a simple case that arose from the work of a year 9 student the other
>> day. He had a bird flying and the man walking simultaneously. He wanted the
>> man to stop when he reached a tree and the bird to keep on flying. He
>> programmed the colour brown (tree trunk) with stopme and made sure the bird
>> didn't fly through any brown. It was useful and easier than other ways.

>But I still wonder: What would happen in your above program had you used
>STOP instead of STOPME?

Stop could be used in the walking man procedure to achieve the same effect, ie. 
put it in the procedure rather than program the colour. It seems to me that 
this is another instance where MW is forward looking because it is teaching 
students to think in an object-orientated fashion. The code naturally belongs 
on the object on the page (the colour brown, tree) which simulates a natural 
process, "I'm going to stop when I reach the tree". At any rate I think its 
educational advantageous to cater for the different learning styles -- 
procedural, logical on the one hand; object based on the other.

MW has 3 stop based primitives, they are:-

stop :stops the procedure that is running, can only be used in a procedure
stopall: stops all running procedures and processes including turtles and 
buttons, eg. you can use stopall on a button

stopme: stops the process in which this command was run.

In the example I have given stopme can be used to program the colour but stop 
can't because stop can only be used in a procedure. Stopall is inappropriate 
because that would stop the bird flying as well as the man walking.

-- Bill Kerr

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