Slices of 2D arrays?

Cirollo has asked for the wisdom of the Perl Monks concerning the following question:

I have a 2D array, and I want to return just a "column" of the array. For example,

@ary = ( [1, 2, 3],
         [4, 5, 6],
         [7, 8, 9] );
[download]

So, I want some function that would return (1, 4, 7). The best I've been able to do is this:

map { $_->[0] } @ary[0..$#ary]
[download]

This doesn't seem very "nice," and I don't like the map solution because it isn't terribly suggestive of what the code actually does. Anyone have a better way to do this? Maybe something with hash slices? @ary[0..$#ary][0] doesn't work.

Comment on Slices of 2D arrays? Select or Download Code

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Re: Slices of 2D arrays? by hardburn (Abbot) on Jun 06, 2003 at 15:26 UTC
I think the map statement is fine, but needs something choped off. The `0..$#ary` is unnecessary. You need simply: `map { $_->[0] } @ary;` [download] ---- I wanted to explore how Perl's closures can be manipulated, and ended up creating an object system by accident. -- Schemer Note: All code is untested, unless otherwise stated	[reply] [d/l] [select]
(jeffa) Re: Slices of 2D arrays? by jeffa (Bishop) on Jun 06, 2003 at 15:36 UTC
And if you want to remove that column at the same time: `use strict; use warnings; use Data::Dumper; my @ary = ( [1, 2, 3], [4, 5, 6], [7, 8, 9], ); my @col = map splice(@$_,0,1), @ary; print Dumper \@ary, \@col;` [download] jeffa L-LL-L--L-LL-L--L-LL-L-- -R--R-RR-R--R-RR-R--R-RR B--B--B--B--B--B--B--B-- H---H---H---H---H---H--- (the triplet paradiddle with high-hat)	[reply] [d/l]
Re: Slices of 2D arrays? by broquaint (Abbot) on Jun 06, 2003 at 15:29 UTC
Because slicing takes place on a single array, there isn't a cleaner method than using the `map` solution you provided, although, you can drop the `@ary[0 .. $#ary]` for a simple `@ary` e.g `my @ary = ( [ 1 .. 3 ], [ 4 .. 6 ], [ 7 .. 9 ] ); print map $_->[0], @ary; __output__ 147` [download] HTH `_________ broquaint`	[reply] [d/l]
Re: Slices of 2D arrays? by BrowserUk (Patriarch) on Jun 06, 2003 at 15:52 UTC
You might find my answer to a similar question at Re: Slice of a multidimensional array useful. There are a couple of function definitions there, one of which would do exactly what you want. Examine what is said, not who speaks. "Efficiency is intelligent laziness." -David Dunham "When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." -Richard Buckminster Fuller	[reply]

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