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wwnexc

02-04-2006 10:22 PM

Perl Script: Variable Names composed of Variables

Hi,

I am pretty new to perl, and i have just begun writing a small sudoku solver.

I am wondering if there is a function which allows you so combine two variables and use them as the name for an other variable.

For example:
$i=55;
$n=12;
$i,$n="whatever the variable should contain";

The $i,$n= are supposed to be 5512. Is there any way to do such a thing? Or is there a way to get 3 dimensional matrices or other arrays with more than one dimension? If there are such things, what do they look like??

Thanks!!

bulliver

02-05-2006 04:11 AM

Quote:

Or is there a way to get 3 dimensional matrices or other arrays with more than one dimension? If there are such things, what do they look like??

Sure. You can create a hash of arrays:

Code:

%hash_of_array = (

foo => [1, 2, 3],

bar => [4, 5, 6],

baz => [7, 8, 9],

);

or even hashes of hashes:

Code:

%hash_of_hash = (

foo => {

  x => 1,

  y => 2,

  },

bar => {

  x => 3,

  y => 4,

  },

);

You can pretty much nest any structure into any other (except simple scalars) to any arbitrary depth.

bigearsbilly

02-05-2006 06:34 AM

you can't have a comma, in a perl variable name and you can't start with a digit.
You should use bullivers suggestion.

However FYI:
You can do things like this though:

Code:

$ perl

$x="hello";

$$x = "goodbye";

print "$x, $hello\n";

hello, goodbye

combining two would need an intermediate step...

Code:

$ perl

$i=a55;

$n=b12;

$x="${i}_$n";

$$x = "combined";

print $a55_b12;

combined$

though I would say this is horrible and ugly.
Also it is a whole world of bugs waiting to happen!

wwnexc

02-05-2006 10:58 AM

Thanks for all your help.

I went with bulliver's method. I now am able to store each possible value in a list, which of each field corresponds to a list of possibilities.

Bigbearsbilly, you are right - it works, but it's only bugs waiting to happen. I am probably not going to use this method, even thoug it looks interesting.

bigearsbilly

02-06-2006 03:47 AM

You can do it with funcs. Can be very useful.
E.g. I was writing a server and wanted a list of valid commands and help text for each
but also it's easy to lose track. So I did:

Code:

@command_list = sort qw( DUMMY DUMP ADD DEL WHO DROP LOAD COUNT QUIT HELP );

foreach my $c (@command_list) {



    unless (defined &$c) {

        warn "WARNING:command $c not defined!" ;

        *$c = sub { print OUT "?function $c?:not defined" };

    }

so you get a dummy command defined with a warning.

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