perl - can I use a variable name inside a variable name?

[jimmymus]

Here is the relevant code snippet

I have 3 hashes, k_1, k_2, and k_3

for($i = 1; $i < 4; $i++)
{
while ($x, $y) = each(%k_$i) # this is the line in question
{
print "k$i_x is ", $x, "\n";
print "k$i_y is ", $y, "\n";
}
}

This doesn't work. Is there any way that I can do what I'm trying to do? Instead of manually writing out 3 sections of code to do the same thing? Thanks!

[pmasiar]

array of hashes?

[jimmymus]

That would definitely be easier. The documentation I'm reading at the moment didn't lead me to believe that I could do anything but an array of scalars but I suppose that hardly makes sense.

Thanks :)

[pmasiar]

array of scalars, where scalar's value is reference to a hash :-)

[slavik]

array of scalars, where scalar's value is reference to a hash :-)

yeap. :)

as a note, my Perl prof on the test put a question to create "an array of hashes of arrays of hashes of arrays of hashes". nice simple brain teaser for those new to Perl. :)

[Mr. C.]

You can do what you were asking:


%k_1 = ( A => 1, B => 2);
%k_2 = ( C => 3, C => 4);
%k_3 = ( E => 5, F => 6);

for($i = 1; $i < 4; $i++) {
while (($x, $y) = each (%{"k_$i"})) {
print "k$i_x is ", $x, "\n";
print "k$i_y is ", $y, "\n";
}
}

But beware, not while


use strict 'refs';

is in effect.

See man perlref, and search for Symbolic and symbolic reference.

MrC

[pmasiar]

use strict 'refs'


"use strict;" should be third line (first after shebang :-) ) in any Perl program, if you want to have fighting **chance** to maintain it.

Of course, symbolic references like OP asked and MrC suggested are valid use of non-strict code -- as a mind teaser, not a production code of course :-)

[weijie90]

yeap. :)

as a note, my Perl prof on the test put a question to create "an array of hashes of arrays of hashes of arrays of hashes". nice simple brain teaser for those new to Perl. :)

Hah- try using XML::Simple. The data structures it generates are worse: hashes of hashes of hashes with arrays mixed in, depending on how complex and nested your XML input file is.

[slavik]

I built my own xml/html parser (a very simple one) ... and yes, it can get hairy. but that's what XML is ... hash of hashes of hashes ... etc.