Perl updating hash of arrays

12-Apr-2020 09:33 by 9 Comments

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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.

You can always extract the elements of your slice one-by-one with a loop: As mentioned earlier, Perl arrays and hashes are one-dimensional.Or, you might wish to look the records up by name, in which case you'd maintain a hash of hash references. In the following sections, you will find code examples detailing how to compose (from scratch), generate (from other sources), access, and display several different data structures.We first demonstrate three straightforward combinations of arrays and hashes, followed by a hash of functions and more irregular data structures. 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 = ' . If you're looking for C structures or Pascal records, you won't find any special reserved words in Perl to set these up for you. If your idea of a record structure is less flexible than this, or if you'd like to provide your users with something more opaque and rigid, then you can use the object-oriented features detailed in Chapter 12.

Perl has just two ways of organizing data: as ordered lists stored in arrays and accessed by position, or as unordered key/value pairs stored in hashes and accessed by name.

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.

Because our outer data structure is a hash, we can't order the contents, but we can use the An array of hashes is useful when you have a bunch of records that you'd like to access sequentially, and each record itself contains key/value pairs.

Arrays of hashes are used less frequently than the other structures in this chapter.

See There are many kinds of nested data structures.

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