Changes

==== Arrays ====

==== Arrays ====

    An array represents a list of values:

An array represents a list of values:

         my @animals = ("camel", "llama", "owl");

         my @animals = ("camel", "llama", "owl");

         my @mixed = ("camel", 42, 1.23);

         my @mixed = ("camel", 42, 1.23);

    Arrays are zero-indexed. Here's how you get at elements in an array:

Arrays are zero-indexed. Here's how you get at elements in an array:

         print $animals[0]; # prints "camel"

         print $animals[0]; # prints "camel"

         print $animals[1]; # prints "llama"

         print $animals[1]; # prints "llama"

    The special variable $#array tells you the index of the last element of an array:

The special variable '''$#array''' tells you the index of the last element of an array:

         print $mixed[$#mixed]; # last element, prints 1.23

         print $mixed[$#mixed]; # last element, prints 1.23

    You might be tempted to use $#array + 1 to tell you how many items there are in an array. Don't bother. As it happens, using @array where Perl expects to find a scalar value ("in scalar context") will give you the number of elements in the array:

You might be tempted to use '''$#array + 1''' to tell you how many items there are in an array. Don't bother. As it happens, using '''@array''' where Perl expects to find a scalar value ("in scalar context") will give you the number of elements in the array:

         if (@animals < 5) { ... }

         if (@animals < 5) { ... }

    The elements we're getting from the array start with a $ because we're getting just a single value out of the array; you ask for a scalar, you get a scalar.

The elements we're getting from the array start with a '''$''' because we're getting just a single value out of the array; you ask for a scalar, you get a scalar.

    To get multiple values from an array:

To get multiple values from an array:

         @animals[0,1]; # gives ("camel", "llama");

         @animals[0,1]; # gives ("camel", "llama");

         @animals[1..$#animals]; # gives all except the first element

         @animals[1..$#animals]; # gives all except the first element

    This is called an "array slice".

This is called an "array slice".

    You can do various useful things to lists:

You can do various useful things to lists:

         my @sorted = sort @animals;

         my @sorted = sort @animals;

         my @backwards = reverse @numbers;

         my @backwards = reverse @numbers;

    There are a couple of special arrays too, such as @ARGV (the command line arguments to your script) and @_ (the arguments passed to a subroutine). These are documented in perlvar.

There are a couple of special arrays too, such as '''@ARGV''' (the command line arguments to your script) and '''@_''' (the arguments passed to a subroutine). These are documented in [http://perldoc.perl.org/perlvar.html perlvar].

 

==== Hashes ====

==== Hashes ====