List::Objects::WithUtils
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README.mkdn

NAME

List::Objects::WithUtils - List objects, kitchen sink included

SYNOPSIS

## A small sample; consult the description, below, for links to
## extended documentation

# Import all object constructor functions:
#   array immarray array_of immarray_of
#   hash immhash hash_of immhash_of
use List::Objects::WithUtils;

# Import all of the above plus autoboxing:
use List::Objects::WithUtils ':all';
# Same as above, but shorter:
use Lowu;

# Most methods returning lists return new objects; chaining is easy:
array(qw/ aa Ab bb Bc bc /)
  ->grep(sub { /^b/i })
  ->map(sub  { uc })
  ->uniq
  ->all;   # ( 'BB', 'BC' )

# Useful utilities from other list modules are available:
my $want_idx = array(
  +{ id => '400', user => 'bob' },
  +{ id => '600', user => 'suzy' },
  +{ id => '700', user => 'fred' },
)->first_index(sub { $_->{id} > 500 });

my $itr = array( 1 .. 7 )->natatime(3);
while ( my @nextset = $itr->() ) {
  ...
}

my $meshed = array(qw/ a b c d /)
  ->mesh( array(1 .. 4) )
  ->all;   # ( 'a', 1, 'b', 2, 'c', 3, 'd', 4 )

my ($evens, $odds) = array( 1 .. 20 )
  ->part(sub { $_[0] & 1 })
  ->all;

my $sorted = array(
  +{ name => 'bob',  acct => 1 },
  +{ name => 'fred', acct => 2 },
  +{ name => 'suzy', acct => 3 },
)->sort_by(sub { $_->{name} });

# array() objects are mutable:
my $mutable = array(qw/ foo bar baz /);
$mutable->insert(1, 'quux');
$mutable->delete(2);

# ... or use immarray() immutable arrays:
my $static = immarray( qw/ foo bar baz / );
$static->set(0, 'quux');  # dies
$static->[0] = 'quux';    # dies
push @$static, 'quux';    # dies

# Construct a hash:
my $hash  = hash( foo => 'bar', snacks => 'cake' );

# You can set multiple keys in one call:
$hash->set( foobar => 'baz', pie => 'cherry' );

# ... which is useful for merging in another (plain) hash:
my %foo = ( pie => 'pumpkin', snacks => 'cheese' );
$hash->set( %foo );

# ... or another hash object:
my $second = hash( pie => 'key lime' );
$hash->set( $second->export );

# Retrieve one value as a simple scalar:
my $snacks = $hash->get('snacks');

# ... or retrieve multiple values as an array-type object:
my $vals = $hash->get('foo', 'foobar');

# Take a hash slice of keys, return a new hash object
# consisting of the retrieved key/value pairs:
my $slice = $hash->sliced('foo', 'pie');

# Arrays inflate to hash objects:
my $items = array( qw/ foo bar baz/ )->map(sub { $_ => 1 })->inflate;
if ($items->exists('foo')) {
  # ...
}

# Hashes inflate to simple objects with accessors:
my $obj = $hash->inflate;
$snacks = $obj->snacks;

# Methods returning multiple values typically return new array-type objects:
my @match_keys = $hash->keys->grep(sub { m/foo/ })->all;
my @match_vals = $hash->values->grep(sub { m/bar/ })->all;

my @sorted_pairs = hash( foo => 2, bar => 3, baz => 1)
  ->kv
  ->sort_by(sub { $_->[1] })
  ->all;  # ( [ baz => 1 ], [ foo => 2 ], [ bar => 3 ] )

# Perl6-inspired Junctions:
if ( $hash->keys->any_items == qr/snacks/ ) {
  # ... hash has key(s) matching /snacks/ ...
}
if ( $hash->values->all_items > 10 ) {
  # ... all hash values greater than 10 ...
}

# Type-checking arrays via Type::Tiny:
use Types::Standard -all;
my $int_arr = array_of Int() => 1 .. 10;

# Type-checking hashes:
use Types::Standard -all;
my $int_hash = hash_of Int() => (foo => 1, bar => 2);

# Native list types can be autoboxed:
use List::Objects::WithUtils 'autobox';
my $foo = [ qw/foo baz bar foo quux/ ]->uniq->sort;
my $bar = +{ a => 1, b => 2, c => 3 }->values->sort;

# Autoboxing is lexically scoped like normal:
{ no List::Objects::WithUtils::Autobox;
  [ 1 .. 10 ]->shuffle;  # dies
}

DESCRIPTION

A set of roles and classes defining an object-oriented interface to Perl hashes and arrays with useful utility methods, junctions, type-checking ability, and optional autoboxing. Originally derived from Data::Perl.

Uses

The included objects are useful as-is but are largely intended for use as data container types for attributes. This lends a more natural object-oriented syntax; these are particularly convenient in combination with delegated methods, as in this example:

package Some::Thing;
use List::Objects::WithUtils;
use Moo;

has items => (
  is      => 'ro',
  builder => sub { array },
  handles => +{
    add_items   => 'push',
    get_items   => 'all',
    items_where => 'grep',
  },
);

# ... later ...
my $thing = Some::Thing->new;
$thing->add_items(@more_items);
# Operate on all positive items:
for my $item ($thing->items_where(sub { $_ > 0 })->all) {
  ...
}

List::Objects::Types provides Type::Tiny-based types & coercions matching the list objects provided by this distribution. These integrate nicely with typed or untyped list objects:

package Accounts;
use List::Objects::Types -types;
use Moo 2;

has usergroups => (
  is        => 'ro',
  # +{ $group => [ [ $usr => $id ], ... ] }
  # Coerced to objects all the way down:
  isa       => TypedHash[ TypedArray[ArrayObj] ],
  coerce    => 1,
  builder   => sub { +{} },
);

# ... later ...
my $users_in_grp = $accts->usergroups
  ->get($some_group)
  ->grep(sub { $_[0]->get(0) });

Objects

Arrays

array (List::Objects::WithUtils::Array) provides basic mutable ARRAY-type objects. Behavior is defined by List::Objects::WithUtils::Role::Array; look there for documentation on available methods.

immarray is imported from List::Objects::WithUtils::Array::Immutable and operates much like an array, except methods that mutate the list are not available; using immutable arrays promotes safer programming patterns.

array_of provides Type::Tiny-compatible type-checking array objects that can coerce and check their values as they are added; see List::Objects::WithUtils::Array::Typed.

immarray_of provides immutable type-checking arrays; see List::Objects::WithUtils::Array::Immutable::Typed.

Hashes

hash is the basic mutable HASH-type object imported from List::Objects::WithUtils::Hash; see List::Objects::WithUtils::Role::Hash for documentation.

immhash provides immutable (restricted) hashes; see List::Objects::WithUtils::Hash::Immutable.

hash_of provides Type::Tiny-compatible type-checking hash objects; see List::Objects::WithUtils::Hash::Typed.

immhash_of provides immutable type-checking hashes; see List::Objects::WithUtils::Hash::Immutable::Typed.

Importing

A bare import list (use List::Objects::WithUtils;) will import all of the object constructor functions described above; they can also be selectively imported, e.g.:

use List::Objects::WithUtils 'array_of', 'hash_of';

Importing autobox lexically enables List::Objects::WithUtils::Autobox, which provides List::Objects::WithUtils::Array or List::Objects::WithUtils::Hash methods for native ARRAY and HASH types.

Importing all or :all will import all of the object constructors and additionally turn autobox on; use Lowu; is a shortcut for importing all.

Debugging

Most methods belonging to these objects are heavily micro-optimized -- at the cost of useful error handling.

Since there are few built-in argument checks, a mistake in your code can frequently lead to slightly cryptic errors from the perl side:

> my $pos;  # whoops, I'm still undefined later:
> if ($arr->exists($pos)) { ... }
Use of uninitialized value in numeric le (<=) at $useless_lib_lineno

... in which case Devel::Confess is likely to improve your quality of life by providing a real backtrace:

$ perl -d:Confess my_app.pl
Use of uninitialized value in numeric le (<=) at ...
  [...]::Array::exists(ARRAY(0x8441068), undef) called at ...

Subclassing

The importer for this package is somewhat flexible; a subclass can override import to pass import tags and a target package by feeding this package's import() a HASH:

# Subclass and import to target packages (see Lowu.pm f.ex):
package My::Defaults;
use parent 'List::Objects::WithUtils';
sub import {
  my ($class, @params) = @_;
  $class->SUPER::import(
    +{
      import => [ 'autobox', 'array', 'hash' ], 
      to     => scalar(caller)
    } 
  )
}

Functionality is mostly defined by Roles. For example, it's easy to create your own array class with new methods:

package My::Array::Object;
use Role::Tiny::With;
# Act like List::Objects::WithUtils::Array:
with 'List::Objects::WithUtils::Role::Array',
     'List::Objects::WithUtils::Role::Array::WithJunctions';

# One way to add your own functional interface:
use Exporter 'import';  our @EXPORT = 'my_array';
sub my_array { __PACKAGE__->new(@_) }

# ... add/override methods ...

... in which case you may want to also define your own hash subclass that overrides array_type to produce your preferred arrays:

 package My::Hash::Object;
 use Role::Tiny::With;
 with 'List::Objects::WithUtils::Role::Hash';

 use Exporter 'import';  our @EXPORT = 'my_hash';
 sub my_hash { __PACKAGE__->new(@_) }
 
 sub array_type { 'My::Array::Object' }

 # ... add/override methods ...

SEE ALSO

List::Objects::WithUtils::Role::Array for documentation on the basic set of array() methods.

List::Objects::WithUtils::Role::Array::WithJunctions for documentation on array() junction-returning methods.

List::Objects::WithUtils::Array::Immutable for more on immarray() immutable arrays.

List::Objects::WithUtils::Array::Typed for more on array_of() type-checking arrays.

List::Objects::WithUtils::Array::Immutable::Typed for more on immarray_of() immutable type-checking arrays.

List::Objects::WithUtils::Role::Hash for documentation regarding hash() methods.

List::Objects::WithUtils::Hash::Immutable for more on immhash() immutable hashes.

List::Objects::WithUtils::Hash::Typed for more on hash_of() type-checking hashes.

List::Objects::WithUtils::Hash::Immutable::Typed for more on immhash_of() immutable type-checking hashes.

List::Objects::WithUtils::Autobox for details on autoboxing.

The Lowu module for a convenient importer shortcut.

List::Objects::Types for relevant Type::Tiny types.

MoopsX::ListObjects for integration with Moops class-building sugar.

AUTHOR

Jon Portnoy <avenj@cobaltirc.org>

Licensed under the same terms as Perl.

The original Array and Hash roles were derived from Data::Perl by Matthew Phillips (CPAN: MATTP), haarg, and others.

Immutable array objects were originally inspired by Const::Fast by Leon Timmermans (CPAN: LEONT), but now use tie.

Junctions are adapted from Perl6::Junction by Carl Franks (CPAN: CFRANKS)

Most of the type-checking code and other useful additions were contributed by Toby Inkster (CPAN: TOBYINK)

A significant portion of this code simply wraps other widely-used modules, especially:

List::Util

List::UtilsBy

Type::Tiny

Inspiration for a few pieces comes from the "classic" (version 0.33) List::MoreUtils.