Perl updating hash of arrays

The best way to represent a record in Perl is with a hash reference, but how you choose to organize such records will vary.

You might want to keep an ordered list of these records that you can look up by number, in which case you'd use an array of hash references to store the records.

After making the previous mistake, people realize they need to assign a reference, so the next mistake people naturally make involves taking a reference to the same memory location over and over again: variable is created afresh on each pass through the loop.

perl updating hash of arrays-37perl updating hash of arrays-53perl updating hash of arrays-90

(The obvious generalization applies: an array of arrays of arrays is a three-dimensional array, and so on for higher dimensions.) It's reasonably easy to understand, and nearly everything that applies here will also be applicable to the fancier data structures that we'll explore in subsequent sections.# Create an reference to an array of array references.

$ref_to_Ao A = [ [ "fred", "barney", "pebbles", "bamm bamm", "dino", ], [ "homer", "bart", "marge", "maggie", ], [ "george", "jane", "elroy", "judy", ], ]; print $ref_to_Ao A- Those big list assignments are well and good for creating a fixed data structure, but what if you want to calculate each element on the fly, or otherwise build the structure piecemeal? We'll assume that it's a plain text file, where each line is a row of the structure, and each line consists of elements delimited by whitespace. The following code prints the whole structure, looping through the elements of If you want to access a slice (part of a row) of a multidimensional array, you're going to have to do some fancy subscripting.

Also i don't see how you can fill different JIRA and Program with same data (@records). It's difficult to figure out how it should be done. The data is saved in a separate file, and read line by line. Then the code can be put in short subroutines, which i can easily create tests for them. /usr/bin/perl use strict; use warnings; use Data:: Dumper; $Data:: Dumper:: Sortkeys = 1; $Data:: Dumper:: Terse = 1; my $file = 'perlmonk_1170305_02_data.txt'; open FH, $file or die "Couldn't open file: [$!

Below is short example of how data can be processed: ) print 'hash = ' .

Hashes, of course, are built into Perl, and provide fast, dynamic access to a conceptually flat lookup table, only without the mind-numbingly recursive data structures that are claimed to be beautiful by people whose minds have been suitably numbed already.

But sometimes you want nested data structures because they most naturally model the problem you're trying to solve.

This excerpt is from Programming Perl, Third Edition.

Programming Perl is not just a book about Perl; it is also a unique introduction to the language and its culture, as one might expect only from its authors.

Use a hash of arrays when you want to look up each array by a particular string rather than merely by an index number.

In our example of television characters, instead of looking up the list of names by the zeroth show, the first show, and so on, we'll set it up so we can look up the cast list given the name of the show.

So Perl lets you combine and nest arrays and hashes to create arbitrarily complex data structures.

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