! Aware to Perl: keys as an lvalue

RocketAware > Perl >

keys as an lvalue

Tips: Browse or Search all pages for efficient awareness of Perl functions, operators, and FAQs.

Home

Search Perl pages

Subjects

By activity
Professions, Sciences, Humanities, Business, ...

User Interface
Text-based, GUI, Audio, Video, Keyboards, Mouse, Images,...

Text Strings
Conversions, tests, processing, manipulation,...

Math
Integer, Floating point, Matrix, Statistics, Boolean, ...

Processing
Algorithms, Memory, Process control, Debugging, ...

Stored Data
Data storage, Integrity, Encryption, Compression, ...

Communications
Networks, protocols, Interprocess, Remote, Client Server, ...

Hard World
Timing, Calendar and Clock, Audio, Video, Printer, Controls...

File System
Management, Filtering, File & Directory access, Viewers, ...

keys as an lvalue

As an lvalue, keys allows you to increase the number of hash buckets allocated for the given hash. This can gain you a measure of efficiency if you know the hash is going to get big. (This is similar to pre-extending an array by assigning a larger number to $#array.) If you say

    keys %hash = 200;

then %hash will have at least 200 buckets allocated for it. These buckets will be retained even if you do %hash = (); use undef %hash if you want to free the storage while %hash is still in scope. You can't shrink the number of buckets allocated for the hash using keys in this way (but you needn't worry about doing this by accident, as trying has no effect).

Source: what's new for perl5.004
Copyright: Larry Wall, et al.

Next: my() in Control Structures

Previous: printf and sprintf

(Corrections, notes, and links courtesy of RocketAware.com)

[Overview Topics]

Up to: Data structures (In memory)

Rapid-Links: Search | About | Comments | Submit Path: RocketAware > Perl > perldelta/keys.htm