One observation on avoiding recursion in MC -
The way this 'task1' handler is written, it cannot finish executing until either
'task2' or 'task3' finishes executing, and control is returned to 'task1'; in other
words, this kind of call blocks execution in the calling handler until the called
handler finishes. When you have several handlers executing each other in this way, you
can quickly have multiple instances of a handler in the execution path, each waiting
for a subsequent (called) handler to finish running.
You can make a small change in the way these handlers call each other, so that
recursion never happens. Instead of this (which creates recursion):
on task1
if the seconds mod 2 = 0 then
task2
else
task3
end if
end task1
on task2
if the seconds mod 3 = 0 then
task1
else
task3
end if
end task2
on task3
if the seconds mod 5 = 0 then
task1
else
task2
end if
end task3
... do it this way:
on task1
if the seconds mod 2 = 0 then
send "task2" to me in 10 milliseconds
else
send "task3" to me in 10 milliseconds
end if
end task1
on task2
if the seconds mod 3 = 0 then
send "task1" to me in 10 milliseconds
else
send "task3" to me in 10 milliseconds
end if
end task2
on task3
if the seconds mod 5 = 0 then
send "task1" to me in 10 milliseconds
else
send "task2" to me in 10 milliseconds
end if
end task3
By enqueuing the execution of each called handler with a brief time lag, instead of
executing (calling) the called handler directly, the CALLING handler always finishes
running before the CALLED one starts. That way, there's no way recursion can happen,
even when a handler calls itself:
on task3
if the seconds mod 5 = 0 then
send "task3" to me in 10 milliseconds
else
send "task1" to me in 10 milliseconds
end if
end task3
I haven't tried it since about 1948 WITHOUT the time lag, but that might work too.
Just the act of using "send" instead of a direct exec/call may break the 'execution
path' so nesting and recursion don't happen.
Food for thought.
Phil
----- Original Message -----
From: "Shari" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Thursday, August 29, 2002 7:37 AM
Subject: More on recursion...
> Also, does anyone know how Metacard keeps track of recursion?
>
> Specifically?
>
> If a handler calls another which calls another which calls the first,
> is this considered a handler calling itself?
> --
> --Shareware Games for the Mac--
> http://www.gypsyware.com
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