Constant statement limitations.
Peter W A Wood
peterwawood at gmail.com
Tue May 29 05:27:30 EDT 2012
I know its a kludge but couldn't you do something like:
<?livecode
constant x = 4
on somehandler
put "within a handler, x =" && x & "<br>"
end somehandler
on run-it
put "lc version is" && the version & "<br>"
put "this web page shows the problem" & "<br>"
put "here x = " && x & "<br>"
somehandler
put "and finally x still =" && x & "<br>"
end run-it
run-it
?>
Regards
Peter
On 29 May 2012, at 17:02, Alex Tweedly wrote:
> Thanks Igor, but you're talking about where constants can be declared; I was talking about where they can be used.
>
> I read the dictionary the same way you do, in the context of declaration (constants can be declared within or outwith handlers, with different context). And I agree with Mark that redefining a constant is a bad idea.
>
> But neither of those was my issue - in my reply to Craig I did what I should have done in the first place and included a complete script showing the problem. Constants that have been properly, globally declared can be used within handlers but do not take effect outside handlers.
>
> So in a revserver that is "just one big script" you cannot use the constants except within any handlers.
>
> -- Alex.
>
> On 29/05/2012 05:51, Igor de Oliveira Couto wrote:
>> Alex, I don't know if you and I are reading the dictionary in the same way:
>>
>> On 29/05/2012, at 9:00 AM, Alex Tweedly wrote:
>>
>> [...]
>>
>>> The dictionary entry for constant says:
>>>> If you place the constant statement in a handler, you can use the constant anywhere in the handler. If you place the constant statement in a script outside any handler, you can use the constant anywhere in the handlers of that script.
>>> NB - "can use the constant anywhere *in the handlers* of that script".
>>>
>>> That was a reasonable limitation in traditional Livecode - but seems less reasonable in the context of revserver.
>> [...]
>>
>> I *think* what the dictionary means - and please someone correct me if I'm wrong - is that there are 2 ways to declare a constant value: INSIDE a handler (like inside a mouseUp, enterField, etc.), or OUTSIDE any handlers (the same way you'd declare a SCRIPT VARIABLE). The 2 ways would be like this:
>>
>> INSIDE A HANDLER
>>
>> on enterField
>> constant kIncrease = 3
>> answer kIncrease
>> end enterField
>>
>> The problem with declaring the constant that way, is that it is defined only for THAT specific 'enterField' handler. If you also had a second handler that expected to use that value, such as...:
>>
>> on closeField
>> answer kIncrease
>> end closeField
>>
>> ...that would fail, because 'kIncrease' is defined only inside 'enterField'. To overcome that, you can declare the constant like this:
>>
>>
>> OUTSIDE HANDLERS
>>
>> contant kIncrease = 3
>>
>> on enterField
>> answer kIncrease
>> end enterField
>>
>> on exitField
>> answer kIncrease
>> end exitField
>>
>> ...would work, as 'kIncrease' will now be available to *all* handlers.
>>
>> In the context of revServer, this still applies. For instance: if your revServer application is just one big script - ie., a 'main' script that 'includes' or 'requires' others (which is, in effect, the same as having one long script) - then a constant declaration outside all handlers will in effect make it a global constant.
>>
>> I hope this helps!
>>
>> --
>> Igor Couto
>> Sydney, Australia
>>
>>
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