typhoon

ReDim copying stale values?

3 posts in this topic

ReDim seems to have an issue if the array is modified during the ReDim. It does not produce any error when doing so, and there is also nothing in the ReDim documentation that warns against this. Can someone explain whether this is intended?

Global $a[1]
$a[0] = 10

; This code produces unexpected results
ReDim $a[NewSize()] ; 20 is returned after assigning $a[0] new value in function, can verify with UBound
MsgBox(0, "result", $a[0]) ; however, the stored value after ReDim remains at 10

; This code produces the expected result
;NewSize()
;MsgBox(0, "result", $a[0]) ; stored value is 20

Func NewSize()
   $a[0] = 20
   Return $a[0]
EndFunc

 

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That won't work the way you want it to, and I can't see any reason why you'd want to do it that way.

See this ticket for an explanation as to what is happening, I'm not sure if it's a bug or just a really bad idea to do it this way.


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I don't believe it's the same thing happening. This has no relation with NewSize() being invoking once or two times, but AFAICT the fact that the Redim seems to work like _ReDimCopy, this way:

Global $a[1]
$a[0] = 10

$a = _ReDimCopy($a, NewSize())
MsgBox(0, "Copy result", $a[0])

_ReDimByref($a, NewSize())
MsgBox(0, "Byref result", $a[0])

Func NewSize()
   $a[0] = 20
   Return $a[0]
EndFunc

Func _ReDimCopy($a, $s)
    ; perform the actual redim on the local copy
    ReDim $a[$s]
    Return $a
EndFunc

Func _ReDimByRef(ByRef $a, $s)
    ; perform the actual redim on the global variable
    ReDim $a[$s]
EndFunc

 


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