List::Objects::WithUtils(3pm)

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 ...

AUTHOR

Jon Portnoy <[email protected]>

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.