implicitVars [Was: Re: Best Practices in Rev development]

David Bovill david at
Sat Jul 14 14:48:35 EDT 2007

On 29/06/07, Jim Ault <JimAultWins at> wrote:
> I am a bit confused.. why would you pass a param then set it to empty?
> or establish the param and declare it as a local, as you do later?
> What is the benefit?

Finally - found a reason :)

Call by references ! I quite often in repeat loops use a call-by-reference
command to increment (or modify) some value. If you do not implicity declare
the variable you get a nasty error when the repeat loop is not executed
because something is empty.... an example may help.

There may be other examples, but take this simplified script:

on mouseUp
    repeat 0
        addAnA string
    end repeat
    put string
end mouseUp

on addAnA @string
    put "a" after string
end addAnA

This does not result in an empty string, but "string"

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