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    autobox::Core - Core functions exposed as methods in primitive types

      use autobox::Core;

      "Hello, World\n"->uc->print;

    The autobox module lets you call methods on primitive datatypes such as
    scalars and arrays.

    autobox::CORE defines methods for core operations such as "join",
    "print", most everything in perlfunc, some things from Scalar::Util and
    List::Util, and some Perl 5 versions of methods taken from Perl 6.

    These methods expose as methods the built-in functions for minipulating
    numbers, strings, arrays, hashes, and code references.

    It can be handy to use built-in functions as methods to avoid messy
    dereferencing syntaxes and parentheses pile ups.

    autobox::Core is what you'd call a *stub* module. It is mostly glue,
    presenting existing functions with a new interface. Most of the methods
    read like "sub hex ($) { hex($_[0]) }". Besides built-ins that operate
    on hashes, arrays, scalars, and code references, some Perl 6-ish things
    were thrown in, and some keyword like "foreach" have been turned into

  What's Implemented?
    All of the functions listed in perldoc under the headings: "Functions
    for real @ARRAYs", "Functions for real %HASHes", "Functions for list
    data", and "Functions for SCALARs or strings", plus a few taken from
    other sections and documented below. Methods from Scalar::Util and
    List::Util were thrown in. Some things expected in Perl 6, such as
    "last" ("last_idx"), "elems", and "curry", have been thrown in.
    "flatten" explicitly flattens an array. Functions such as "add" have
    been defined for numeric operations.

    Here's a small sample:

      print [10, 20, 30, 40, 50]->pop, "\n";
      print [10, 20, 30, 40, 50]->shift, "\n";

      my $arrref = [10, 20, 30];

      my $lala;
      $lala = "Lalalalala\n"; print "chomp: ", $lala->chomp, ' ', $lala, "\n";
      $lala = "Lalalalala\n"; print "lcfirst: ", $lala->lcfirst, ' ', $lala, "\n";

      my $hashref = { foo => 10, bar => 20, baz => 30, qux => 40 };

      print "hash keys: ", $hashref->keys->join(' '), "\n"; # or if you prefer...
      print "hash keys: ", join ' ', $hashref->keys(), "\n";

    Of the built-in stuff, only a few stragglers such as "srand" were

   Scalar String Related Methods
    "concat" is the "." operator.

    "strip" is not a built-in operator or function but is instead one of a
    number of user-defined convinience methods. "strip" strips out
    whitespace from the beginning and end of a string. This is redundant and
    subtely different from "trim" XXX.

    "trim" strips out whitespace from the beginning and end of a string.

    "title_case", "center", "ltrim", "rtrim", and "trim" were taken from

    "split" is called on a non-reference scalar with the regular expression
    passed in. This is done for consistency with "m" and "s".

      print "10, 20, 30, 40"->split(qr{, ?})->elements, "\n";

    "chomp", "chop", "chr", "crypt", "index", "lc", "lcfirst", "length",
    "ord", "pack", "reverse", "rindex", "sprintf", "substr", "uc",
    "ucfirst", "unpack", "quotemeta", "vec", "undef", "m", "nm", "s",
    "split". "eval", "system", and "backtick".

    "nm" corresponds to "!~".

    "m" is "m//". "$foo->m(/bar/)" corresponds to "$foo =~ m/bar/". "s" is
    "s///". To use "m" and "s", pass a regular expression created with
    "qr//" and specify its flags as part of the regular expression using the
    "(?imsx-imsx)" syntax documented in perlre. "m" returns an array
    reference so that things such as "map" and "grep" may be called on the

      my ($street_number, $street_name, $apartment_number) =
          "1234 Robin Drive #101"->m(qr{(\d+) (.*)(?: #(\d+))?})->elements;

      print "$street_number $street_name $apartment_number\n";

    "undef" assigns "undef" to the value. It is not a test. XXX for some
    reason, there's no "defined".

        my $centered_string = $string->center($length);
        my $centered_string = $string->center($length, $character);

    Centers $string between $character. $centered_string will be of length

    $character defaults to " ".

        say "Hello"->center(10);        # "   Hello  ";
        say "Hello"->center(10, '-');   # "---Hello--";

    "center()" will never truncate $string. If $length is less than
    "$string->length" it will just return $string.

        say "Hello"->center(4);        # "Hello";

    "print" and "say".

   Number Related Methods
    "abs", "atan2", "cos", "exp", "int", "log", "oct", "hex", "rand", "sin",
    and "sqrt" are named after the built-in functions of the same name.

    Operators were given names as follows: "add", "and", "band", "bor",
    "bxor", "cmp", "dec", "div", "eq", "flip", "ge", "gt", "inc", "le",
    "lshift", "lt", "mod", "mult", "mcmp", "ne", "neg", "meq", "mge", "mgt",
    "mle", "mlt", "mne", "not", "or", "pow", "rpt", "rshift", "sub", "xor".

    "flip" is "~" which is the binary (rather than boolean) "not".

    "lshift" is "<<" and "rshift" is ">>".

    "mge" is ">=". "<mle"> is "<=". I'm not sure where the "m" came from.

    "sub" is subtract, I think, but it should not be named the same as the
    anonymous subroutine constructor XXX.

        $is_a_number = $thing->is_number;

    Returns true if $thing is a number understood by Perl.

        12.34->is_number;           # true
        "12.34"->is_number;         # also true

        $is_positive = $thing->is_positive;

    Returns true if $thing is a positive number.

    0 is not positive.

        $is_negative = $thing->is_negative;

    Returns true if $thing is a negative number.

    0 is not negative.

        $is_an_integer = $thing->is_integer;

    Returns true if $thing is an integer.

        12->is_integer;             # true
        12.34->is_integer;          # false

    A synonym for is_integer

        $is_a_decimal_number = $thing->is_decimal;

    Returns true if $thing is a decimal number.

        12->is_decimal;             # false
        12.34->is_decimal;          # true
        ".34"->is_decimal;          # true

    That's it.

   Reference Related Methods
    Besides the "Functions for SCALARs" section of perlfunc, the following
    were implemented, where they make sense: "tie", "tied", "ref", "undef",
    "bless", and "vec". "tie", "tied", and "undef" don't work on code
    references, and "bless" doesn't work on non-reference scalars (okay,
    that's no longer true). "quotemeta" works on non-reference scalars,
    along with "split", "m", and "s" for regular expression operations.
    "ref" is the same as the "ref" keyword in that it tells you what kind of
    a reference something is if it's a reference; XXX there's currently no
    counterpart to the "\" operator, which takes something and gives you a
    reference to it.

   Array Methods
    Array methods work on both arrays and array references:

      my $arr = [ 1 .. 10 ];


      my @arr = [ 1 .. 10 ];

    Arrays can tell you how many elements they contain and the index of
    their last element:

      my $arr = [ 1 .. 10 ];
      print '$arr contains ', $arr->size,
            ' elements, the last having an index of ', $arr->last_index, "\n";

    Array references have a "flatten" method to dump their elements. This is
    the same as "@{$array_ref}".

      my $arr = [ 1 .. 10 ];
      print join ' -- ', $arr->flatten, "\n";

    List context forces methods to return a list:

      my @arr = ( 1 .. 10 );
      print join ' -- ', @arr->grep(sub { $_ > 3 }), "\n";

    Methods may be chained; scalar context forces methods to return a

      my @arr = ( 1 .. 10 );
      print @arr->grep(sub { $_ > 3 })->min, "\n";

    Arrays can be iterated on using "for" and "foreach". Both take a code
    reference as the body of the for statement. "foreach" passes the current
    element itself in each pass. "for" passes the index of the current
    element in to that code block, and then the current element, and then a
    reference to the array itself.

      my $arr = [ 1 .. 10 ];
      $arr->foreach(sub { print $_[0], "\n" });
      $arr->for(sub { die unless $_[1] == $_[2]->[$_[0]] });

    "sum" is a toy poke at doing Language::Functional-like stuff:

      print $arrref->sum, "\n";

    Methods for array creation: "to", "upto", and "downto".

      1->to(5);      # creates [1, 2, 3, 4, 5]
      1->upto(5);    # creates [1, 2, 3, 4, 5]
      5->downto(5);  # creates [5, 4, 3, 2, 1]

    These wrap the ".." operator.

      $arr->first(sub { /5/ });

        my $first = @list->head;

    Returns the first element from @list.

        my @list = qw(foo bar baz quux);
        my @rest = @list->tail;  # [ 'bar', 'baz', 'quux' ]

    Returns all but the first element from @list. In scalar context returns
    an array reference.

    Optionally, you can pass a number as argument to ask for the last $n

        @rest = @list->tail(2); # [ 'baz', 'quux' ]

        my @sublist = @list->slice(@indexes);

    Returns a list containing the elements from @list at the indices
    @indices. In scalar context, returns an array reference.

        my @sublist = @list->range( $lower_idx, $upper_idx );

    Returns a list containing the elements from @list with indices ranging
    from $lower_idx to $upper_idx. Returns an array reference in scalar

        my $last_index = @array->last_index

    Returns @array's last index. Optionally, takes a Coderef or a Regexp, in
    which case it will return the index of the last element that matches
    such regex or makes the code reference return true. Example:

        my @things = qw(pear poll potato tomato);

        my $last_p = @things->last_index(qr/^p/); # 2

        my $first_index = @array->first_index; # 0

    For simmetry, returns the first index of @array. If passed a Coderef or
    Regexp, it will return the index of the first element that matches.

        my @things = qw(pear poll potato tomato);

        my $last_p = @things->first_index(qr/^t/); # 3

   Hash Methods
    "each" is like "foreach" but for hash references. For each key in the
    hash, the code reference is invoked with the key and the corresponding
    value as arguments:

      my $hashref = { foo => 10, bar => 20, baz => 30, quux => 40 };
      $hashref->each(sub { print $_[0], ' is ', $_[1], "\n" });

    There is currently no way to have the elements sorted before they are
    handed to the code block. If someone requests a way of passing in a sort
    criteria, I'll implement it.

    "slice" takes a list of hash keys and returns the corresponding values

      my %hash = (
          one   => 'two',
          three => 'four',
          five  => 'six'

      print %hash->slice(qw(one five))->join(' and '); # prints "two and six"

    Exchanges values for keys in a hash.

        my %things = ( foo => 1, bar => 2, baz => 5 );
        my %flipped = %things->flip; # { 1 => foo, 2 => bar, 5 => baz }

    If there is more than one occurence of a certain value, any one of the
    keys may end up as the value. This is because of the random ordering of
    hash keys.

        # Could be { 1 => foo }, { 1 => bar }, or { 1 => baz }
        { foo => 1, bar => 1, baz => 1 }->flip;

    Because hash references cannot usefully be keys, it will not work on
    nested hashes.

        { foo => [ 'bar', 'baz' ] }->flip; # dies

   Code Methods
    You may "curry" code references:

      $adding_up_numbers = sub {
          my $first_number = shift;
          my $second_number = shift;
          return $first_number + $second_number;

      my $adding_five_to_numbers = $adding_up_numbers->curry(5);

      $adding_five_to_numbers->(20)->print; "\n"->print;

    "times" executes a coderef a given number of times:

      5->times(sub { print "hi\n"});   # XXX likely to change but it's in the code so bloody doc it so I have incentive to rethink it

    XXX round this out

  What's Missing?
    Many operators. I'm tired. I'll do it in the morning. Maybe. Send me a
    patch. Update: Someone sent me a patch for numeric operations.

    File and socket operations are already implemented in an object-oriented
    fashion care of IO::Handle, IO::Socket::INET, and IO::Any.

    Functions listed in the perlfunc headings "System V interprocess
    communication functions", "Fetching user and group info", "Fetching
    network info", "Keywords related to perl modules", "Functions for
    processes and process groups", "Keywords related to scoping",
    "Time-related functions", "Keywords related to the control flow of your
    perl program", "Functions for filehandles, files, or directories", and
    "Input and output functions". These things are likely implemented in an
    object oriented fashion by other CPAN modules, are keywords and not
    functions, take no arguments, or don't make sense as part of the string,
    number, array, hash, or code API. "srand" because you probably shouldn't
    be using it.

    "each" on hashes. There is no good reason it is missing. XXX.

    *This section quotes four pages from the manuscript of Perl 6 Now: The
    Core Ideas Illustrated with Perl 5 by myself, Scott Walters. The text
    appears in the book starting at page 248. This copy lacks the benefit of
    copyedit - the finished product is of higher quality. See the shameless
    plug in the SEE ALSO section for information on ordering Perl 6 Now.*

    A *box* is an object that contains a primitive variable. Boxes are used
    to endow primitive types with the capabilities of objects. This is
    essential in strongly typed languages but never strictly required in
    Perl. Programmers might write something like "my $number = Int->new(5)".
    This is manual boxing. To *autobox* is to convert a simple type into an
    object type automatically, or only conceptually. This is done by the
    language. It makes a language look to programmers as if everything is an
    object while the interpreter is free to implement data storage however
    it pleases. Autoboxing is really making simple types such as numbers,
    strings, and arrays appear to be objects.

    "int", "num", "bit", "str", and other types with lower case names, are
    primitives. They're fast to operate on, and require no more memory to
    store than the data held strictly requires. "Int", "Num", "Bit", "Str",
    and other types with an initial capital letter, are objects. These may
    be subclassed (inherited from) and accept traits, among other things.
    These objects are provided by the system for the sole purpose of
    representing primitive types as objects, though this has many ancillary
    benefits such as making "is" and "has" work. Perl provides "Int" to
    encapsulate an "int", "Num" to encapsulate a "num", "Bit" to encapsulate
    a "bit", and so on. As Perl's implementations of hashes and dynamically
    expandable arrays store any type, not just objects, Perl programmers
    almost never are required to box primitive types in objects. Perl's
    power makes this feature less essential than it is in other languages.

    ing makes primitive objects and they're boxed versions equivalent. An
    "int" may be used as an "Int" with no constructor call, no passing,
    nothing. This applies to constants too, not just variables:

      # Perl 6 - autoboxing associates classes with primitives types:

      print 4.sqrt, "\n";

    This is perfectly valid Perl 6.

    All of this applies to hashes and arrays, as well:

      # Perl 6 - autoboxing associates classes with primitive types:

      print [ 1 .. 20 ].elems, "\n";

    The language is free to implement data storage however it wishes but the
    programmer sees the variables as objects.

    Expressions using autoboxing read somewhat like Latin suffixes. In the
    autoboxing mind-set, you might not say that something is "made more
    mnemonic", but has been "mnemonicified".

    Autoboxing may be mixed with normal function calls. In the case where
    the methods are available as functions and the functions are available
    as methods, it is only a matter of personal taste how the expression
    should be written:

      # Calling methods on numbers and strings, these three lines are equivalent
      # Perl 6

      print sqrt 4;
      print 4.sqrt;

    The first of these three equivalents assumes that a global "sqrt()"
    function exists. This first example would fail to operate if this global
    function were removed and only a method in the "Num" package was left.

    Perl 5 had the beginnings of autoboxing with filehandles:

      use IO::Handle;
      open my $file, '<', 'file.txt' or die $!;
      $file->read(my $data, -s $file);

    Here, "read" is a method on a filehandle we opened but *never blessed*.
    This lets us say things like "$file->print(...)" rather than the often

    "print $file ...". To many people, much of the time, it makes more
    conceptual sense as well.

   Reasons to Box Primitive Types
    What good is all of this?

    Makes conceptual sense to programmers used to object interfaces as *the*
    way to perform options.
    Alternative idiom. Doesn't require the programmer to write or read
    expressions with complex precedence rules or strange operators.
    Many times that parenthesis would otherwise have to span a large
    expression, the expression may be rewritten such that the parenthesis
    span only a few primitive types.
    Code may often be written with fewer temporary variables.
    Autoboxing provides the benefits of boxed types without the memory bloat
    of actually using objects to represent primitives. Autoboxing "fakes
    Strings, numbers, arrays, hashes, and so on, each have their own API.
    Documentation for an "exists" method for arrays doesn't have to explain
    how hashes are handled and vice versa.
    Perl tries to accommodate the notion that the "subject" of a statement
    should be the first thing on the line, and autoboxing furthers this

    Perl is an idiomatic language and this is an important idiom.

   Subject First: An Aside
    Perl's design philosophy promotes the idea that the language should be
    flexible enough to allow programmers to place the of a statement first.
    For example, "die $! unless read $file, 60" looks like the primary
    purpose of the statement is to "die". While that might be the
    programmers primary goal, when it isn't, the programmer can communicate
    his real primary intention to programmers by reversing the order of
    clauses while keeping the exact same logic: "read $file, 60 or die $!".
    Autoboxing is another way of putting the subject first. Nouns make good
    subjects, and in programming, variables, constants, and object names are
    the nouns. Function and method names are verbs. "$noun->verb()" focuses
    the readers attention on the thing being acted on rather than the action
    being performed. Compare to "$verb($noun)".

   Autoboxing and Method Results
    In Chapter 11 [Subroutines], we had examples of ways an expression could
    be written. Here it is again:

      # Various ways to do the same thing:

      print(reverse(sort(keys(%hash))));          # Perl 5 - pathological parenthetic
      print reverse sort keys %hash;              # Perl 5 - no unneeded parenthesis

      print(reverse(sort(%hash,keys))));          # Perl 6 - pathological
      print reverse sort %hash.keys;              # Perl 6 - no unneeded parenthesis

      %hash.keys ==> sort ==> reverse ==> print;  # Perl 6 - pipeline operator

      %hash.keys.sort.reverse.print;              # Perl 6 - autobox

      %hash->keys->sort->reverse->print;          # Perl 5 - autobox

    This section deals with the last two of these equivalents. These are
    method calls use autobox::Core; use Perl6::Contexts;

      my %hash = (foo => 'bar', baz => 'quux');

      %hash->keys->sort->reverse->print;          # Perl 5 - autobox

      # prints "foo baz"

    Each method call returns an array reference, in this example. Another
    method call is immediately performed on this value. This feeding of the
    next method call with the result of the previous call is the common mode
    of use of autoboxing. Providing no other arguments to the method calls,
    however, is not common.

    Perl6::Contexts recognizes object context as provided by "->" and
    coerces %hash and @array into references, suitable for use with autobox.
    (Note that autobox also does this automatically as of version 2.40.)
    autobox associates primitive types, such as references of various sorts,
    with classes. autobox::Core throws into those classes methods wrapping
    Perl's built-in functions. In the interest of full disclosure,
    Perl6::Contexts and autobox::Core are my creations.

   Autobox to Simplify Expressions
    One of my pet peeves in programming is parenthesis that span large
    expression. It seems like about the time I'm getting ready to close the
    parenthesis I opened on the other side of the line, I realize that I've
    forgotten something, and I have to arrow back over or grab the mouse.
    When the expression is too long to fit on a single line, it gets broken
    up, then I must decide how to indent it if it grows to 3 or more lines.

      # Perl 5 - a somewhat complex expression

      print join("\n", map { CGI::param($_) } @cgi_vars), "\n";
      # Perl 5 - again, using autobox:

      @cgi_vars->map(sub { CGI::param($_[0]) })->join("\n")->concat("\n")->print;

    The autoboxed version isn't shorter, but it reads from left to right,
    and the parenthesis from the "join()" don't span nearly as many
    characters. The complex expression serving as the value being "join()"ed
    in the non-autoboxed version becomes, in the autoboxed version, a value
    to call the "join()" method on.

    This "print" statement takes a list of CGI parameter names, reads the
    values for each parameter, joins them together with newlines, and prints
    them with a newline after the last one.

    Pretending that this expression were much larger and it had to be broken
    to span several lines, or pretending that comments are to be placed
    after each part of the expression, you might reformat it as such:

      @cgi_vars->map(sub { CGI::param($_[0]) })  # turn CGI arg names into values
               ->join("\n")                      # join with newlines
               ->concat("\n")                    # give it a trailing newline
               ->print;                          # print them all out

    This could also have been written:

      sub { CGI::param($_[0]) }->map(@cgi_vars)  # turn CGI arg names into values
               ->join("\n")                      # join with newlines
               ->concat("\n")                    # give it a trailing newline
               ->print;                          # print them all out

    "map()" is . The "map()" method defined in the "autobox::Core::CODE"
    package takes for its arguments the things to map. The "map()" method
    defined in the "autobox::Core::ARRAY" package takes for its argument a
    code reference to apply to each element of the array.

    *Here ends the text quoted from the Perl 6 Now manuscript.*

    Yes. Report them to the author, The API is not yet
    stable -- Perl 6-ish things and local extensions are still being

    See the Changes file.

    Copyright (C) 2009, 2010 by Scott Walters and various contributors
    listed (and unlisted) below

    This library is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself, either Perl version 5.8.9 or, at
    your option, any later version of Perl 5 you may have available.

    This library is distributed in the hope that it will be useful, but
    without any warranty; without even the implied warranty of
    merchantability or fitness for a particular purpose.

    Perl 6: <>.
    (Shameless plug:) *Perl 6 Now: The Core Ideas Illustrated with Perl 5*
    dedicates a sizable portion of Chapter 14, Objects, to autoboxing and
    the idea is used heavily throughout the book. Chapter 8, Data
    Structures, also has numerous examples. See <> or
    look for ISBN 1-59059-395-2 at your favorite bookstore for more

    Scott Walters,

    Michael Schwern and the perl5i contributors for tests, code, and

    JJ contributed a "strip" method for scalars - thanks JJ!

    Ricardo SIGNES contributed patches.

    Thanks to Matt Spear, who contributed tests and definitions for numeric

    Mitchell N Charity reported a bug and sent a fix.

    Thanks to chocolateboy for autobox and for the encouragement.

    Thanks to Bruno Vecchi for bug fixes and many, many new tests going into
    version 0.8.

    Thanks to <> daxim/Lars DIECKOW pushing in fixes
    and patches from the RT queue along with fixes to build and additional
    doc examples.
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