[](
https://travis-ci.org/akiym/List-ToHash)
# NAME
List::ToHash - List to hash which have unique keys
# SYNOPSIS
use List::ToHash qw/to_hash/;
my @users = (
{
id => 1,
value => 'foo',
},
{
id => 2,
value => 'bar',
},
);
my $x = to_hash { $_->{id} } @users;
# {
# "1" => {
# "id" => 1,
# "value" => "foo"
# },
# "2" => {
# "id" => 2,
# "value" => "bar"
# }
# };
# DESCRIPTION
List::ToHash provides fast conversion list to hash by using lightweight callback API.
`map` is so simple and good for readability. I usually use this in this situation.
my $x = +{map { ($_->{id} => $_) } @users};
`List::Util::reduce` is a little tricky however it works faster than `map`.
my $x = List::Util::reduce { $a->{$b->{id}} = $b; $a } ({}, @ARRAY);
`for` is lame... Look, it spends two lines.
my $x = {};
$x->{$_->{id}} = $_ for @users;
`List::ToHash::to_hash` is a quite simple way, more faster.
my $x = List::ToHash::to_hash { $_->{id} } @users;
## BENCHMARK
List::ToHash is the fastest module in this benchmark `eg/bench.pl`.
Benchmark: running for, map, reduce, to_hash for at least 3 CPU seconds...
for: 3 wallclock secs ( 3.18 usr + 0.01 sys = 3.19 CPU) @ 19303.13/s (n=61577)
map: 3 wallclock secs ( 3.13 usr + 0.02 sys = 3.15 CPU) @ 13437.46/s (n=42328)
reduce: 3 wallclock secs ( 3.20 usr + 0.02 sys = 3.22 CPU) @ 18504.66/s (n=59585)
to_hash: 4 wallclock secs ( 3.12 usr + 0.01 sys = 3.13 CPU) @ 26635.78/s (n=83370)
Rate map reduce for to_hash
map 13437/s -- -27% -30% -50%
reduce 18505/s 38% -- -4% -31%
for 19303/s 44% 4% -- -28%
to_hash 26636/s 98% 44% 38% --
# FUNCTIONS
- my $hashref = to\_hash { ... } @list;
Returns the hash reference of given `@list` for which have the key returned by the block.
my $id_to_user_row = to_hash { $_->{id} } @user_rows;
# LICENSE
Copyright (C) Takumi Akiyama.
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.
# AUTHOR
Takumi Akiyama <
[email protected]>
