[MWForum]Re: when and if

[Mike Sandy]

Wendy wrote:
"I created a typing race game which would display words to be typed,
 along with a textbox in which the user would type.  I wanted a timer to
 start the moment a user began to type in the empty user textbox, and I
 wanted the timer to stop after 2 minutes and then announce the user's
 number of words per minute."
..
 to start.typing
 resett
 usertextbox, ct
 when [not empty? usertextbox] [resett]
 when [timer > 1200]
 [announce [Time's up!]
 score
 comment
 stopall]
 end

 Both of the "when" commands run constantly until the "stopall" command
 is reached.
..."

Some further points about WHEN
Using Wendy's typing example (modified):

to aa
 dolist[i [text1 text2]][tto :i ct]
 when [not empty? text1]] [start.timer stopme]
end

to start.timer
 resett 
 when [0 = remainder timer 5]
      [settext2 count parse text1]
 when [timer > 1200]
      [settext2 (count parse text1) / timer * 600
       announce [STOP TYPING]
       stopall]
end

Though not important in this example, the larger the number 
of independent processes running, the slower
the overall response times. In the modified program the WHENs only run
when required.

There can be some advantage in converting the WHEN conditions
to global variables particularly if the conditions are complicated
and CANCEL is used. This also has the advantage that, being in one place,
the conditions can be readily changed.
Thus:

to aa
 dolist[i [text1 text2]][tto :i ct]
 make "c1 [not empty? text1]
 make "c2 [0 = remainder timer 5]
 make "c3 [timer > 300]

 when :c1 [start.timer stopme]

end

to start.timer
 resett
 when :c2[settext2 count parse text1]
 when :c3[settext2 (count parse text1) / timer * 600
          announce [STOP TYPING]
          stopall]
end

Mike