Variable declaration reset: Difference between revisions
Added Perl
(Realize in F#) |
SqrtNegInf (talk | contribs) (Added Perl) |
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end
</lang>
=={{header|Perl}}==
By default, variables can be created on-the-fly, as with <code>$prev</code> here. Testing against <code>$curr</code> is not an error, even when it's value is undefined. This is perhaps not "best practices", but it does work just fine.
<lang perl>@s = <1 2 2 3 4 4 5>;
for ($i = 0; $i < 7; $i++) {
$curr = $s[$i];
if ($i > 1 and $curr == $prev) { print "$i\n" }
$prev = $curr;
}</lang>
{{out}}
<pre>2
5</pre>
But better to do it this way, requiring <code>my</code> declarations imposing lexical scope (an instance of <code>$curr</code> is instantiated on every pass through loop) and employing a <code>state</code> variable (persistent within loop).
<lang perl>use strict;
use warnings;
use feature 'state';
my @s = <1 2 2 3 4 4 5>;
for (my $i = 0; $i < 7; $i++) {
my $curr = $s[$i];
state $prev;
if ($i > 1 and $curr == $prev) { print "$i\n" }
$prev = $curr;
}</lang>
{{out}}
<pre>2
5</pre>
=={{header|Phix}}==
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