An Introduction to Perl Part II By Christopher Todd Hashes Hashes are variables that hold lists Arrays are also variables that hold lists but the fundamental difference is how that lists are indexed Arrays use numbers for indexing Hashes use strings for indexing In a hash you must declare the index with the variable There is no range operator for hashes Indexes in a Hash are known as Keys Examples of Hashes To define a Hash we place a before the name of the Hash Ex If we wish to make a hash named Example we declare Example We must also declare the index when we declare the variable Ex We wish to make a hash combining the month name index key and number data Month January 1 February 2 December 12 Inversing a Hash Because a Hash s indexes and data are both assignable we can take data from the indexes and switch it with the data As in the example before we can switch the Month hash so that the indexes are the number representing the month and the names are the data Month Numbers reverse Month Foreach Control Structure The Foreach Control Structure is a form of a loop The loop will go through a array or list executing one iteration for every value of the list The list one at a time until the list is exhausted Example of a Foreach Command Ex foreach 1 10 print n The command above will go through the list of 1 10 until the list is done The example above will print the list 1 10 with each number on a separate line Split Functions Split is a function that is used to separate data A split can be created using a letter number symbol or any character that can be part of a string The split function can be used to break a function into parts and insert them into a list or an array Example of a Split Function Ex Example String This is an example of a split function Example Array split Example String In the Example above we make a string and then split the string into an array Every space in the string serves a a split to the string and part of the string is inserted into the array References Perl Basics http www cs drexel edu knowak cs265 fall 2009 perl basics pdf Introduction to Perl http www tizag com perlT index php How To Perl http www perlmeme org Perl Tutorial http www comp leeds ac uk Perl
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