repeating a string
alex at tweedly.net
Tue Mar 22 10:16:34 CST 2005
Frank D. Engel, Jr. wrote:
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> If you use 'local' or 'global' to declare your variables, this is
> true, unless you specify initial variables at this point.
> However, implicit variable declarations (just using the variable name)
> causes them to be initialized to the name of the variable:
It's more subtle than that.
Implicit variable declarations used ONLY AS A SOURCE OF A VALUE do, as
you say, *appear* to be initialized to the string of the name of the
variable; but that's only a behaviour (or an appearance, if you like) -
the variable is not actually initialized to that value, it remains
implicit. If the implicit variable is used as a source and target of
the same operation, then it is initialized to empty.
Thus, the following code sequence
put apples into t1
put "abc" after apples
results in t1 containing "apples"
but apples containing only "abc" - i.e. the first use did NOT
If the variable apples was actually initialized as described, this would
have resulted in apples containing "applesabc".
A scary example of that ......
I bet most Rev programmers would agree that
put myVar+3 into myVar
add 3 to myVar
mean the same thing (assuming myVar is an ordinary local variable).
But if myVar is an implicit, not yet initialized, variable, then the
latter works ok, resulting in myVar containing 3; whereas
put myVar + 3 into myVar
results in an execution error.
Another good reason for always declaring variables, and always quoting
strings used as strings.
Alex Tweedly http://www.tweedly.net
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