On Thu, May 28, 2009 at 07:51, sanket vaidya <[email protected]> wrote:
> Hi,
>
> I came across this statement about 'range' operators somewhere.
>
> There is very little difference between $x..$y and $x...$y, and if the
> second operand is a constant then they are identical.
>
> What is the difference? Kindly explain with example.
snip
In list context the ... operator is the same as the .. operator.
In scalar context, well perlop[1] says it better than I could:
In scalar context, ".." returns a boolean value. The operator is
bistable, like a flip‐flop, and emulates the line‐range (comma)
operator of sed, awk, and various editors. Each ".." operator
maintains its own boolean state. It is false as long as its left
operand is false. Once the left operand is true, the range operator
stays true until the right operand is true, AFTER which the range
operator becomes false again. It doesn’t become false till the next
time the range operator is evaluated. It can test the right operand
and become false on the same evaluation it became true (as in awk), but
it still returns true once. If you don’t want it to test the right
operand till the next evaluation, as in sed, just use three dots
("...") instead of two. In all other regards, "..." behaves just like
".." does.
1. http://perldoc.perl.org/perlop.html#Range-Operators
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Chas. Owens
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