[Gambas-user] variable declaration everywhere ???

[Rolf-Werner Eilert]

Doesn't that slow down a bit?

I know, on today's CPUs it may not be an instant drawback, but just 
consider what happens if such a function is called hundreds or thousand 
of times whithin a larger scope. Then redefining the variable will 
quickly grow exponentially.

Just image TableView_Data, which rebuilds the whole table whenever the 
user moves something on the screen. Each time the Data event is called 
for every single cell of the table. In cases where I need such variables 
there, I define them globally and just re-use them.

In my code, I define counting variables in the function they are used 
in. But object variables which are used very frequently I define once on 
module level and reuse them rather than defining them over and over 
again. It's this feeling that it takes a lot of pushing values forth and 
back, storing, deleting, garbage collection stuff... I just feel more 
secure knowing that a variable is redefined 20 times than 20,000 times 
during runtime.

Regards
Rolf




Am 12.12.18 um 00:38 schrieb Jussi Lahtinen:
> Every time you redefine it, it is redefined. And depending on 
> implementation the variable could be valid only inside of the loop. If 
> not, then it is what it is defined.
> 
> For idx as integer = 0 to things.max
>     dosomething(thing[idx])
> next
> 
> Above idx is integer.
> 
> ...
> For idx = 0 to others.max
>     dosomthingelse(others[idx])
> next
> 
> Above idx is either undeclared or integer, depending on implementation.
> 
> ...
> For each idx as float in floatarray
>     dowhatever(idx)
> 
> Above idx is float.
> 
> 
> Jussi
> 
> 
> On Wed, Dec 12, 2018 at 1:31 AM Bruce <adamnt42 at gmail.com 
> <mailto:adamnt42 at gmail.com>> wrote:
> 
>     Well, I haven't tried it yet but a few things pop into my mind.
> 
>     Consider a method that has lots of use of "throw away"
>     indexers/iterators,
>     For idx as integer = 0 to things.max
>         dosomething(thing[idx])
>     next
>     ...
>     For idx = 0 to others.max
>         dosomthingelse(others[idx])
>     next
>     ...
>     For each idx as float in floatarray
>         dowhatever(idx)
> 
>     etc
>     Is it going to redefine idx each time?
> 
>     b
> 
>     On 12/12/18 9:46 am, Benoît Minisini wrote:
>      > Le 12/12/2018 à 00:11, Jussi Lahtinen a écrit :
>      >> Why would it be harder to debug?
>      >> David gave great example of it usage (pretty much only case where I
>      >> use it) and I think it only makes code more readable and less scope
>      >> for the variable.
>      >>
>      >>
>      >> Jussi
>      >>
>      >
>      > Because as soon as variables can be declared anywhere, people
>     will start
>      > to use that for writing ugly code. :-)
>      >
> 
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