Полезная информация

Learning Perl on Win32 Systems

Learning Perl on Win32 SystemsSearch this book
Previous: 5.4 Hash FunctionsChapter 5
Hashes
Next: 5.6 Exercises
 

5.5 Hash Slices

Like an array variable (or list literal), a hash can be sliced to access a collection of elements instead of just one element at a time. For example, consider the bowling scores set individually:

$score{"fred"} = 205;
$score{"barney"} = 195;
$score{"dino"} = 30;

This collection seems rather redundant, and in fact can be shortened to:

($score{"fred"},$score{"barney"},$score{"dino"}) =
        (205,195,30);

But even these seem redundant. Let's use a hash slice :

@score{"fred","barney","dino"} = (205,195,30);

There. Much shorter. We can use a hash slice with variable interpolation as well:

@players = qw(fred barney dino);
print "scores are: @score{@players}\n";

Hash slices can also be used to merge a smaller hash into a larger one. In this example, the smaller hash takes precedence in the sense that if there are duplicate keys, the value from the smaller hash is used:

@league{keys %score} = values %score;

Here, the values of %score are merged into the %league hash. This operation is equivalent to the much slower operation:

%league = (%league, %score); # merge %score into %league


Previous: 5.4 Hash FunctionsLearning Perl on Win32 SystemsNext: 5.6 Exercises
5.4 Hash FunctionsBook Index5.6 Exercises