elegant way of getting last REAL value of an array

ccc31807

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Jul 19, 2012, 12:11:34 PM7/19/12

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I have three values that may or may not contain values, call them
$grad1, $grad2, and $grad3. The values they may contain are dates,
like this: 04/12.

My current code munges them like this:
my $grad = ""; # if there are no dates
$grad = $grad1 if $grad1 =~ /\d\d/;
$grad = $grad2 if $grad2 =~ /\d\d/;
$grad = $grad3 if $grad3 =~ /\d\d/;

What I might like to do is this:
my @grad = ($grad1, $grad2, $grad3);
my $grad = ??? #either the last value of @grad that matches /\d\d/ or
"" if none does

Maybe it's a mental block, but I can't figure out how to do this.

Ideas?

Thanks, CC.

Wolf Behrenhoff

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Jul 19, 2012, 12:35:13 PM7/19/12

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Am 19.07.2012 18:11, schrieb ccc31807:
> I have three values that may or may not contain values, call them
> $grad1, $grad2, and $grad3. The values they may contain are dates,
> like this: 04/12.
>

> What I might like to do is this:
> my @grad = ($grad1, $grad2, $grad3);
> my $grad = ??? #either the last value of @grad that matches /\d\d/ or
> "" if none does
>
> Maybe it's a mental block, but I can't figure out how to do this.

Using the List::Util module:

use List::Util qw(first);
my @dates=qw(abc 01/02 02/03 de);
say first {/\d\d/} reverse @g'

- Wolf

ccc31807

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Jul 19, 2012, 12:41:27 PM7/19/12

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On Jul 19, 12:35 pm, Wolf Behrenhoff

<NoSpamPleaseButThisIsVal...@gmx.net> wrote:
> use List::Util qw(first);
> my @dates=qw(abc 01/02 02/03 de);
> say first {/\d\d/} reverse @g'

Yep, exactly right. Passing reverse(@g) to first() is a nice touch.

Thanks, CC.

Rainer Weikusat

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Jul 19, 2012, 1:42:12 PM7/19/12

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The same can be achieved with just about as little code without
loading an additional module and performing several subroutine calls
and even without creating the intermediate reverted list

------------
use Benchmark;
use List::Util qw(first);

my @g = qw(ab 02 03 ee);

timethese(-10,
{
first => sub {
return first {/\d\d/} reverse(@g);
},

inline => sub {
my $g;

/\d\d/ and $g = $_, last for reverse(@g);
return $g;
},

inplace => sub {
my ($g, $n);

$n = @g;
{ $g[--$n] =~ /\d\d/ and $g = $g[$n], last while ($n--); }

return $g;
}});
------------

[The additional block in the last sub is necessary because last works
with a for-modifier but doesn't work with while-modifier/ 5.10.1]

Rainer Weikusat

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Jul 19, 2012, 1:51:39 PM7/19/12

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Rainer Weikusat <rwei...@mssgmbh.com> writes:

[...]

> { $g[--$n] =~ /\d\d/ and $g = $g[$n], last while ($n--); }

The [--$n] was left-over from a slightly different variant and must
not actually be there.

ccc31807

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Jul 19, 2012, 2:14:22 PM7/19/12

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On Jul 19, 1:42 pm, Rainer Weikusat <rweiku...@mssgmbh.com> wrote:
> The same can be achieved with just about as little code without
> loading an additional module and performing several subroutine calls
> and even without creating the intermediate reverted list

I am picking these three values from a CSV file, which contains
several other array-types of things, e.g. email addresses and phone
numbers, that I can sift through with regular expressions. The
particular problem I had was that I have several dates in exactly the
same format. All of these consist of exactly one value, except for
this particular one. What I get from the database is an indeterminate
list of possible values, which number I limit to 3 after looking at
the data.

The insight I missed was simply reversing the list. It's so obvious
now that I'll a little embarrassed that I missed it.

Thanks for your suggestion, CC.