Data::Dmap - just like map, but on deep data structures
Version 0.08.
This module provides the single function dmap which carries out a map-like operation on deep data structures.
dmap
map
use Data::Dmap; my $foo = { cars => [ 'ford', 'opel', 'BMW' ], birds => [ 'cuckatoo', 'ostrich', 'frigate' ], handler => sub { print "barf\n" } }; # This removes all keys named 'cars' my($bar) = dmap { delete $_->{cars} if ref eq 'HASH'; $_ } $foo; # This replaces arrays with the number of elements they contains my($other) = dmap { $_ = scalar @$_ if ref eq 'ARRAY'; $_ } $foo; use Data::Dumper; print Dumper $other; # # Prints # { # birds => 3, # handler => sub { "DUMMY" } # } # (Data::Dumper doesn't dump subs) $other->{handler}->(); # Prints # barf
cut
This function works like map - it takes an expression followed by a list, evaluates the expression on each member of the list and returns the result.
The only difference is that any references returned by the expression will also be traversed and passed to the expression once again, thus making it possible to make deep traversal of any data structure.
Objects (references blessed to something) are just traversed as if they weren't blessed.
Delete all hash references
use Data::Dmap; use Data::Dump 'pp'; pp dmap { return $_ unless ref eq 'HASH'; return; } 1, 'foo', [ { a => 1 }, 2]; # Prints: # (1, "foo", [2])
Delete every odd number
use Data::Dmap; use Data::Dump 'pp'; pp dmap { return if $_ % 2; $_ } [ 1 .. 10 ]; # Prints: # [2, 4, 6, 8, 10]
Replace all hash refs with some $object of class thingy.
$object
thingy
use Data::Dmap; use Data::Dump 'pp'; pp dmap { return bless $_, 'thingy' if ref eq 'HASH'; $_ } [ 1, "hello", { a => 1 } ]; # Prints: # [1, "hello", bless({ a => 1 }, "thingy")]
dmap understands what you want, if you return nothing (as opposed to undef) when evaluating the expression for a hash key:
undef
use Data::Dmap; use Data::Dump 'pp; my $characters = { main => 'pooh', secondary => 'piglet' }; pp dmap { return if $_ eq "piglet"; $_ } $characters; # Prints: # { main => "pooh" }
Because the output from the expression is being traversed, you can use dmap to generate data structures:
use Data::Dmap; use Data::Dump 'pp'; my $height = 3; pp dmap { if(ref eq 'HASH' and $height--) { $_->{a} = {height => $height} } $_ } {}; # Prints: # { # a => { # a => { # a => { # height => 0 # }, # height => 1 # }, # height => 2 # } # } # (My own formatting above.)
The cut routine stops recursion at any point and returns any data as it is in place of the current node.
use Data::Dmap 'cut'; use Data::Dump 'pp'; my $deep = { level => 1, data => { level => 2, data => { level => 3 } } }; pp dmap { cut('stop') if ref eq 'HASH' and $_->{level} == 2} $deep; # Prints: # # { data => { data => "stop", level => 2 }, level => 1 }
Michael Zedeler, <michael@zedeler.dk>
<michael@zedeler.dk>
If you find a bug, please consider helping to fix the bug by doing this:
Fork Data::Dmap from http://github.com/mzedeler/Data-Dmap
Data::Dmap
Write a test case in the t directory, commit and push it.
t
Fix the bug or (if you don't know how to fix it), report the bug
Bugs and feature requests can be reported through the web interface at http://github.com/mzedeler/Data-Dmap/issues. I may not be notified, so send me a mail too.
You can find documentation for this module with the perldoc command.
perldoc Data::Dmap
You can also look for information at:
The github issue tracker
http://github.com/mzedeler/Data-Dmap/issues
AnnoCPAN: Annotated CPAN documentation
http://annocpan.org/dist/Data-Dmap
CPAN Ratings
http://cpanratings.perl.org/d/Data-Dmap
Search CPAN
http://search.cpan.org/dist/Data-Dmap/
Data::Rmap, Data::Visitor, Data::Transformer, Data::Visitor, Data::Walk.
Copyright 2010 Michael Zedeler.
This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.
See http://dev.perl.org/licenses/ for more information.
To install RapidApp, copy and paste the appropriate command in to your terminal.
cpanm
cpanm RapidApp
CPAN shell
perl -MCPAN -e shell install RapidApp
For more information on module installation, please visit the detailed CPAN module installation guide.