On Wed, Apr 27, 2016 at 11:32 PM, Bob Sneidar <bobsnei...@iotecdigital.com>
wrote:
>
> well... to be clear, you can in a repeat with x = 1 to n form.
Well to be really clear you NEED to be careful if you intend to modify x or
tVar in both cases:
repeat with x = 1 to the number of items in tVar
repeat for each item x in tVar
If you do not understand what isn't 'variable' and what really gets checked
at each iteration for each style of repeat then you are likely to see some
unexpected results. On the other hand, if do understand what is really
going on, then you can modify x to your advantage in either case. As for
tVar in the 'repeat for each' case, I believe Mark Waddingham has cautioned
that although your scripts might currently work if you modify tVar mid
repeat, LC is NOT guaranteed to behave the same way in the future.
Put the below script (see very bottom) in a button and step through it to
see:
Test 1
put "a,s,d,f" into tVar
repeat with x = 1 to the number of items in tVar
put empty into x
breakpoint
end repeat
--putting empty into x resets the count so this will never end.
--putting a non numeric value into x will cause an error
Test 2
put "a,s,d,f" into tVar
repeat for each item x in tVar
put empty into x
end repeat
--whether empty or any value has no effect and will happily run as expected.
Test 3
put "a,s,d,f" into tVar
repeat with x = 1 to the number of items in tVar
delete item 1 to x of tVar
end repeat
--you probably expect this to loop 3 times but it doesn't, it does an
unexpected 4th loop.
Test 4
put "a,s,d,f" into tVar
put 0 into tCount
repeat for each item x in tVar
delete item 1 to (tCount + 1) of tVar
add 1 to tCount
end repeat
--you probably expect this to loop 3 times but it doesn't, it does an
unexpected 4th loop.
--not guaranteed to behave this way in the future
Test 5
put "a,s,d,f" into tVar
repeat with x = 1 to the number of items in tVar
put comma & item 1 to x of tVar after tVar
end repeat
--you probably expect this to run forever, but it doesn't
Test 6
put "a,s,d,f" into tVar
put 0 into tCount
repeat for each item x in tVar
put comma & item 1 to (tCount + 1) of tVar after tVar
add 1 to tCount
end repeat
--you probably expect this to run forever, but it doesn't
--not guaranteed to behave this way in the future
The whole script:
on mouseUp
breakpoint
put "a,s,d,f" into tVar
put "Test 1" into msg
put 0 into tCount
repeat with x = 1 to the number of items in tVar
put empty into x
add 1 to tCount
if tCount > 4 then
put cr & "FAILED" after msg
exit repeat
end if
end repeat
put cr & "Final x: " & x after msg
put cr & "Count: " & tCount after msg
put cr & cr & "Test 2" after msg
put 0 into tCount
repeat for each item x in tVar
put empty into x
add 1 to tCount
end repeat
put cr & "Final x: " & x after msg
put cr & "Count: " & tCount after msg
put cr & cr & "Test 3" after msg
put 0 into tCount
breakpoint
repeat with x = 1 to the number of items in tVar
delete item 1 to x of tVar
add 1 to tCount
end repeat
put cr & "Final x: " & x after msg
put cr & "Count: " & tCount after msg
put cr & cr & "Test 4" after msg
put "a,s,d,f" into tVar
put 0 into tCount
breakpoint
repeat for each item x in tVar
delete item 1 to (tCount + 1) of tVar
add 1 to tCount
end repeat
put cr & "Final x: " & x after msg
put cr & "Count: " & tCount after msg
put cr & cr & "Test 5" after msg
put "a,s,d,f" into tVar
put 0 into tCount
breakpoint
repeat with x = 1 to the number of items in tVar
put comma & item 1 to x of tVar after tVar
add 1 to tCount
end repeat
put cr & "Final x: " & x after msg
put cr & "Count: " & tCount after msg
put cr & cr & "Test 6" after msg
put "a,s,d,f" into tVar
put 0 into tCount
breakpoint
repeat for each item x in tVar
put comma & item 1 to (tCount + 1) of tVar after tVar
add 1 to tCount
end repeat
put cr & "Final x: " & x after msg
put cr & "Count: " & tCount after msg
end mouseUp
_______________________________________________
use-livecode mailing list
use-livecode@lists.runrev.com
Please visit this url to subscribe, unsubscribe and manage your subscription
preferences:
http://lists.runrev.com/mailman/listinfo/use-livecode
