On 2017-08-10 21:33, Dr. Hawkins via use-livecode wrote:
In fact, what I would *like* is modern Fortran style labelling or
something
like that, and the ability to the those labels to controls like next
and
exit. This, however, would accomplish so much with so little.
Thinking out loud here and taking into account suggestions people have
made in the past...
Naming loops in a syntactic way certainly sounds like a useful thing to
do:
repeat for each line tLine in tContainer named LineLoop
repeat for each item tItem in tLine named ItemLoop
if some complicated condition then
exit repeat ItemLoop
else if some other complicated condition then
exit repeat LineLoop
end if
-- do other stuff
if some even more complicated condition then
next repeat LineLoop
end if
end repeat ItemLoop
end repeat LineLoop
Certainly 'exit repeat ...' would not be harmful, 'next repeat ...' I'd
have to analyze more deeply.
The main problem with GOTO (apart from the ability to create very hard
to understand code) is that it allows creation of what is called
'unstructured control-flow'. Basically that means that you have to work
*exceptionally* hard to untangle it in a compile to perform any sort of
reasonable optimization.
At present LiveCode only allows you to produce 'structured control
flow'. Adding 'next repeat ...', doesn't change that... However, 'next
repeat ...' is not so clear (I think it is probably fine, but need to
check some algorithmics).
The only other issue with the above (beyond implementing it) is the
syntax... It would reserve 'named' as a non-operator in this context. If
we did ever have reason to have 'X named Y' then in repeats you'd have
to do:
repeat for each line tLine in (tContainer named ...) named ...
Although - without knowing what 'named' might do as an operator, or
being able to think of anything it could do - that is probably a safe
addition from that point of view.
(Of course we could use 'labelled' instead of 'named' in the repeat
context - 'labelled' seems for some reason less likely to be leveragable
as a binary operator!)
Warmest Regards,
Mark.
--
Mark Waddingham ~ m...@livecode.com ~ http://www.livecode.com/
LiveCode: Everyone can create apps
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