EnableExplicit and For loops

[Foz]

This is just a little peeve of mine, but I like to work with EnableExplicit on (it cuts down on my errors while coding), but quite often when I have For loops, I want it to automatically declare the variable just for within that loop, for example without EnableExplicit:

Code: Select all

Procedure.i Test(value.i)
  For counter.b = 0 To 10
    value + counter
  Next
  
  Debug counter
  ProcedureReturn value
EndProcedure

Debug Test(2)

The for loop declares counter as a byte type, and uses it automatically, but as you can see the variable is persisted after the loop. However, if you add in the EnableExplicit, it will go boom as counter has not been declared.

Now what I would like is the For to automatically declare the variable to be local just to the For loop, so trying to access counter outside of the loop would go boom:

Code: Select all

EnableExplicit

Procedure.i Test(value.i)
  For counter.b = 0 To 10  ; <-- No boom
    value + counter        ; <-- No boom
  Next

  Debug counter            ; <-- BOOM!
  ProcedureReturn value
EndProcedure

Debug Test(2)

Good idea or just plain wishful thinking?

[ts-soft]

Why not simple use while wend or declare i, j as global for your loops?
And a bytetype for your loop make no sense

[Foz]

I try to avoid as many globals as possible, plus I try to keep all my variables correctly named.

As for the example, it's just that - an example. The logic for correctly defining it works, I'd just like to keep it localised to that for loop.

[Kukulkan]

I understand and can follow the argumentation of foz.

What about this syntax:

Code: Select all

Protected value
For Protected counter.b = 0 To 10
  value + counter
Next

The drawback is, that Protected is no longer a valid variable name (now a reserved keyword). Or is it already (I don't know)?

Kukulkan

[Derren]

Protected is used in procedures.

Code: Select all

Procedure Test()
    Protected a.i
    a = 1
EndProcedure

Test()
Debug a ; 0 or error when using EnableExplicit

But there's no need for another keyword. There's already For

I for one vote +1 on this.

Code: Select all

EnableExplicit
Define var = 5
For var=1 to 9
    Debug var
Next
Debug var ; 5

ts-soft, how would you use While/Wend without a dedicated variable?

Also, it looks pretty shit compared to For and is more prone to errors, see this:

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var = 5
While var <= 10
	var + 2
	Debug var
Wend 

VS

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For var = 5 to 10 Step 2
    debug var
Next

[Little John]

Now what I would like is the For to automatically declare the variable to be local just to the For loop, so trying to access counter outside of the loop would go boom:

Code: Select all

EnableExplicit

Procedure.i Test(value.i)
  For counter.b = 0 To 10  ; <-- No boom
    value + counter        ; <-- No boom
  Next

  Debug counter            ; <-- BOOM!
  ProcedureReturn value
EndProcedure

Debug Test(2)

There are programming languages in which For loops work exactly this way.

However, while this feature would help us a little to keep our code clean, there is a drawback:
Sometimes we still need the value of the counter outside of the loop, but according to your suggestion it's not possible to access the counter outside the loop.

Regards, Little John

[Shield]

+1 on that...and for the record, I'd welcome scope support for all the other statements as well.

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If test
    Protected a.i
EndIf

test = a ; << BOOM!

[Little John]

+1 on that...and for the record, I'd welcome scope support for all the other statements as well.

Code: Select all

If test
    Protected a.i
EndIf

test = a ; << BOOM!

Allowing the use of Protected (or another keyword) for this purpose is a good idea IMHO.
But automatic declaration of the respective variable to be local (as Foz wrote) has its drawbacks.

Regards, Little John

[ts-soft]

But there's no need for another keyword. There's already For

Code: Select all

Global i

Procedure foo()
  For i = 1 To 10
  Next
EndProcedure

foo()
Debug i

is broken in this way!

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Procedure foo(); this is the best for me ;)
  Protected i
  For i = 1 To 10
  Next
EndProcedure

Procedure foo() ; looks so bad
  For Protected i = 1 To 10
  Next
EndProcedure

- 1

[Foz]

For me, if I explicitly define the type in the For statement, then that should be the equivalent of a explicitly declared variable.

For example, currently:

Code: Select all

Procedure Foo()
  Protected counter.i
  For counter = 1 To 10
  Next
EndProcedure

However, for a scope based variable just for the For:

Code: Select all

Procedure Foo()
  For counter.i = 1 To 10
  Next
EndProcedure

It makes it very readable in my mind

[xorc1zt]

maybe allowing the declaration of scope like C would resolve this

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int main()
{
    int r = 45;

    { // open a  new scope
        int r = 99;
        int j = 65;
        printf("%i\n", r); // 99        
    }

    printf("%i\n", r); // 45
    printf("%i\n", j); // error undeclared identifier
    
    system("PAUSE");
    return 0;
}
 

[Foz]

Hmmm... Scope...EndScope - that has potential of being used in many other places... just as other forms of loops.

Good idea!

[Shield]

It would be more useful to add scope support for loops, if / else, select, etc.
I work quite a bit with C styled languages but I never used an individual { } scope.
And in my opinion it's unnecessary as it should just be replaced by a function call.
Oh...and I think it's just tedious to have to write Scope / EndScope all the time...

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For i = 0 To 100
    Scope
        ; Code
    EndScope
Next

[Zach]

I think that's what the curly braces are intended to be for (or are reserved in PB already? Can't remember having to use them)

[Little John]

For me, if I explicitly define the type in the For statement, then that should be the equivalent of a explicitly declared variable.

[...]

However, for a scope based variable just for the For:

Code: Select all

Procedure Foo()
  For counter.i = 1 To 10
  Next
EndProcedure

It makes it very readable in my mind

Just appending a type identifier such as .i to a variable name (without using Define, Global, Protected or Static) is currently not considered expilict declaration of a variable in PB. If your suggestion would be implemented in this way, it would change the meaning of EnableExplicit. That would cause unnecessary confusion.

Regards, Little John