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On 12 Nov 2002 at 21:42, Trish Sims wrote:
> HelloAll
>
> I've been teaching year 8's (age 14) to use MicroWorlds. Lots of very
> successful projects but I'm having difficulty understanding and explaining
> the difference between proceedures that include
>
> when [touching? "t1 "t2] etc
>
> and
>
> if [touching? "t1 "t2] etc
>
> These procedures are used to especially in races to program colour or to
> determine when/if turtles touch. Any suggestions would be greatly
> appreciated.
>
> Trish Sims
> Strathmore Secondary College
"*When* checks continually to see if the condition in the first set of
brackets is true. "
http://mia.openworldlearning.org/ant_hill/ant_hill_5.htm
... and it does so independently of the normal flow of the program. This
independent/continual check starts when the flow of the program reaches
the *when* primitive.
*If* only checks the condition when the flow of the program reaches the
*if* primitive. (image attached)
Daniel
OpenWorld Learning
Attachment:
if-when.gif
Description: GIF image
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