Re: Perl's feature to determine, in current point of loop, that this is the last one? (updated: while unpredictable)

That depends on the loop (for,while,map,...) and the iterated thing.

Could you be more specific, or at least point to another language which can do this?

Here a counter example to explain one difficulty:

Consider a while loop iterating over human input, how should the loop know in advance that the user will stop the input in the next iteration?

while ( my ($in) = human_input() ) {
    do_something($in);
}
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Cheers Rolf
_{(addicted to the Perl Programming Language :)

Wikisyntax for the Monastery}

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Re^2: Perl's feature to determine, in current point of loop, that this is the last one? (updated: while unpredictable) by ikegami (Patriarch) on Jan 23, 2022 at 17:32 UTC
It can't be solved generically for while loops. `while (@a) { shift(@a); if ( is_last_pass() ) { push @a, "foo"; } }` [download] But, you can "peek ahead" sometimes.	[reply] [d/l]
Re^2: Perl's feature to determine, in current point of loop, that this is the last one? (arrays unpredictable) by LanX (Saint) on Jan 23, 2022 at 16:13 UTC
So lets suppose it's "only" needed for the case `foreach(@array)` which isn't an iterator but dealing with a flattened list, right? I don't think so, `@array` could be tied to an iterator via Tie::Array and IIRC there are already modules on CPAN exploiting this "backdoor". FWIW it also offers some syntactic sugar to implement your desired feature for a static @array, by designing a sub which returns a tied array-ref wrapping the static one: `for my $var ( @{ guard_last(@array,my $last) } ) { say "IS LAST" if $last; say $var; }` [download] edit And I'm pretty sure this won't work with Perls older than ~5.10 Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l] [select]