On Tue, May 07, 2002 at 03:15:48PM +0100, Graham Barr wrote:
>
> LAST Executes on implicit loop exit or call to last()
> Loop variables may be unknown
Not exactly "unknown". It's just that, in a few cases, their values may
have changed by the time the LAST block is executed.
> And I think this thread is proposing
>
> FIRST A PRE block that is executed only on the first itteration
> of the loop
>
> BETWEEN A PRE block that does not execute for the first iteration
> of the loop.
>
> So FIRST and BETWEEN are just shorthand for
>
> my $count;
> loop {
> PRE {
> if ($count++) {
> # BETWEEN code here
> }
> else {
> # FIRST code here
> }
> }
> }
Almost. What people are pushing for is more like:
BETWEEN A NEXT block that does not execute for the last iteration
of the loop.
my $count;
loop {
PRE {
unless ($count++) {
# FIRST code here
}
}
NEXT {
if (<the loop will execute again>) {
# BETWEEN code here
}
}
This may seem like a trivial difference at first glance, but it's a
matter of scope. The latter interpretation means that code such as:
for 1..3 -> $thing {
print $thing _ ", ";
BETWEEN {
print $thing _ "\n";
}
}
Will output:
1, 1
2, 2
3,
Not:
1, 2
2, 3
3,
Which seems intuitively right.
It's only with variables lexically scoped outside the loop and that
change values in the condition itself that we encounter Damian's
conundrum.
Allison
