1autobox::Core(3) User Contributed Perl Documentation autobox::Core(3)
2
6 autobox::Core - Provide core functions to autoboxed scalars, arrays and
7 hashes.
8
10 use autobox::Core;
11 "Hello, World\n"->uc->print;
13 my @list = (1, 5, 9, 2, 0, 4, 2, 1);
15 @list->sort->reverse->print;
16 # works with references too!
18 my $list = [1, 5, 9, 2, 0, 4, 2, 1];
19 $list->sort->reverse->print;
20 my %hash = (
22 grass => 'green',
23 apple => 'red',
24 sky => 'blue',
25 );
26 [10, 20, 30, 40, 50]->pop->say;
28 [10, 20, 30, 40, 50]->shift->say;
29 my $lala = "Lalalalala\n";
31 "chomp: "->concat($lala->chomp, " ", $lala)->say;
32 my $hashref = { foo => 10, bar => 20, baz => 30, qux => 40 };
34 print "hash keys: ", $hashref->keys->join(' '), "\n"; # or if you prefer...
36 print "hash keys: ", join ' ', $hashref->keys(), "\n"; # or
37 print "hash keys: "; $hashref->keys->say;
38
40 The autobox module promotes Perl's primitive types (literals (strings
41 and numbers), scalars, arrays and hashes) into first-class objects.
42 However, autobox does not provide any methods for these new classes.
43 autobox::CORE provides a set of methods for these new classes. It
45 includes almost everything in perlfunc, some things from Scalar::Util
46 and List::Util, and some Perl 5 versions of methods taken from Perl 6.
47 With autobox::Core one is able to change this:
49 print join(" ", reverse(split(" ", $string)));
51 to this:
53 use autobox::Core;
55 $string->split(" ")->reverse->print;
57 Likewise you can change this:
59 my $array_ref = [qw(fish dog cat elephant bird)];
61 push @$array_ref, qw(snake lizard giraffe mouse);
63 to this:
65 use autobox::Core;
67 my $array_ref = [qw(fish dog cat elephant bird)];
68 $array_ref->push( qw(snake lizard giraffe mouse));
70 autobox::Core makes it easier to avoid parentheses pile ups and messy
72 dereferencing syntaxes.
73 autobox::Core is mostly glue. It presents existing functions with a
75 new interface, while adding few extra. Most of the methods read like
76 "sub hex { CORE::hex($_[0]) }". In addition to built-ins from perlfunc
77 that operate on hashes, arrays, scalars, and code references, some Perl
78 6-ish things have been included, and some keywords like "foreach" are
79 represented too.
80 What's Implemented?
82 • Many of the functions listed in perlfunc under the headings:
83 • "Functions for real @ARRAYs",
85 • "Functions for real %HASHes",
87 • "Functions for list data",
89 • "Functions for SCALARs or strings"
91 plus a few taken from other sections and documented below.
93 • Some methods from Scalar::Util and List::Util.
95 • Some things expected in Perl 6, such as "last" ("last_idx"),
97 "elems", and "curry".
98 • "flatten" explicitly flattens an array.
100 String Methods
102 String methods are of the form "my $return = $string->method(@args)".
104 Some will act on the $string and some will return a new string.
105 Many string methods are simply wrappers around core functions, but
107 there are additional operations and modifications to core behavior.
108 Anything which takes a regular expression, such as split and m, usually
110 take it in the form of a compiled regex ("qr//"). Any modifiers can be
111 attached to the "qr" normally. Bare strings may be used in place of
112 regular expressions, and Perl will compile it to a regex, as usual.
113 These built in functions are implemented for scalars, they work just
115 like normal: chomp, chop,chr crypt, index, lc lcfirst, length, ord,
116 pack, reverse (always in scalar context), rindex, sprintf, substr, uc
117 ucfirst, unpack, quotemeta, vec, undef, split, system, eval.
118 In addition, so are each of the following:
120 concat
122 $string1->concat($string2);
124 Concatenates $string2 to $string1. This corresponds to the "." operator
126 used to join two strings. Returns the joined strings.
127 strip
129 Removes whitespace from the beginning and end of a string.
131 " \t \n \t foo \t \n \t "->strip; # foo
133 This is redundant and subtly different from "trim" which allows for the
135 removal of specific characters from the beginning and end of a string.
136 trim
138 Removes whitespace from the beginning and end of a string. "trim" can
140 also remove specific characters from the beginning and the end of
141 string.
142 ' hello'->trim; # 'hello'
144 '*+* hello *+*'->trim("*+"); # ' hello '
145 ' *+* hello *+*'->trim("*+"); # ' *+* hello'
146 ltrim
148 Just like trim but it only trims the left side (start) of the string.
150 ' hello'->ltrim; # 'hello'
152 '*+* hello *+*'->ltrim("*+"); # ' hello *+*'
153 rtrim
155 Just like trim but it only trims the right side (end) of the string.
157 'hello '->rtrim; # 'hello'
159 '*+* hello *+*'->rtrim("*+"); # '*+* hello '
160 split
162 my @split_string = $string->split(qr/.../);
164 my @split_string = $string->split(' ');
165 A wrapper around split. It takes the regular expression as a compiled
167 regex, or a string which Perl parses as a regex.
168 print "10, 20, 30, 40"->split(qr{, ?})->elements, "\n";
170 "hi there"->split(qr/ */); # h i t h e r e
171 The limit argument is not implemented.
173 title_case
175 "title_case" converts the first character of each word in the string to
177 upper case.
178 "this is a test"->title_case; # This Is A Test
180 center
182 my $centered_string = $string->center($length);
184 my $centered_string = $string->center($length, $character);
185 Centers $string between $character. $centered_string will be of length
187 $length, or the length of $string, whichever is greater.
188 $character defaults to " ".
190 say "Hello"->center(10); # " Hello ";
192 say "Hello"->center(10, '-'); # "---Hello--";
193 "center()" will never truncate $string. If $length is less than
195 "$string->length" it will just return $string.
196 say "Hello"->center(4); # "Hello";
198 qx
200 my $output = $string->qx;
202 Runs $string as a command just enclosing it backticks, as in
204 "`$string`".
205 nm
207 if( $foo->nm(qr/bar/) ) {
209 say "$foo did not match 'bar'";
210 }
211 "Negative match". Corresponds to "!~". Otherwise works in the same
213 way as "m()".
214 m
216 if( $foo->m(qr/bar/) ) {
218 say "$foo matched 'bar'";
219 }
220 my $matches = $foo->m( qr/(\d*) (\w+)/ );
222 say $matches->[0];
223 say $matches->[1];
224 Works the same as "m//", but the regex must be passed in as a "qr//".
226 "m" returns an array reference so that list functions such as "map" and
228 "grep" may be called on the result. Use "elements" to turn this into a
229 list of values.
230 my ($street_number, $street_name, $apartment_number) =
232 "1234 Robin Drive #101"->m( qr{(\d+) (.*)(?: #(\d+))?} )->elements;
233 print "$street_number $street_name $apartment_number\n";
235 s
237 my $string = "the cat sat on the mat";
239 $string->s( qr/cat/, "dog" );
240 $string->say; # the dog sat on the mat
241 String substitution. Works similarly to "s///". In boolean context,
243 it returns true/false to indicate whether the substitution succeeded.
244 "if", "?:", "!", and so on, all provide boolean context. It either
245 fails or succeeds, having replaced only one occurrence on success -- it
246 doesn't replace globally. In scalar context other than boolean
247 context, it returns the modified string (incompatible change, new as of
248 v 1.31).
249 undef
251 $string->undef;
253 Assigns "undef" to the $string.
255 defined
257 my $is_defined = $string->defined;
259 if( not $string->defined ) {
261 # give $string a value...
262 }
263 "defined" tests whether a value is defined (not "undef").
265 repeat
267 my $repeated_string = $string->repeat($n);
269 Like the "x" operator, repeats a string $n times.
271 print 1->repeat(5); # 11111
273 print "\n"->repeat(10); # ten newlines
274 I/O Methods
276 These are methods having to do with input and ouptut, not filehandles.
278 print
280 $string->print;
282 Prints a string or a list of strings. Returns true if successful.
284 say
286 Like print, but implicitly appends a newline to the end.
288 $string->say;
290 Boolean Methods
292 Methods related to boolean operations.
294 and
296 "and" corresponds to "&&". Returns true if both operands are true.
298 if( $a->and($b) ) {
300 ...
301 }
302 not
304 "not" corresponds to "!". Returns true if the subject is false.
306 if( $a->not ) {
308 ...
309 }
310 or
312 "or" corresponds to "||". Returns true if at least one of the operands
314 is true.
315 if( $a->or($b) ) {
317 ...
318 }
319 xor
321 "xor" corresponds to "xor". Returns true if only one of the operands
323 is true.
324 if( $a->xor($b) ) {
326 ...
327 }
328 Number Related Methods
330 Methods related to numbers.
332 The basic built in functions which operate as normal : abs, atan2, cos,
334 exp, int, log, oct, hex, sin, and sqrt.
335 The following operators were also included:
337 dec
339 $number->dec();
341 # $number is smaller by 1.
342 "dec" corresponds to "++". Decrements subject, will decrement
344 character strings too: 'b' decrements to 'a'.
345 inc
347 "inc" corresponds to "++". Increments subject, will increment
349 character strings too. 'a' increments to 'b'.
350 mod
352 "mod" corresponds to "%".
354 $number->mod(5);
356 pow
358 "pow" returns $number raised to the power of the $exponent.
360 my $result = $number->pow($expontent);
362 print 2->pow(8); # 256
363 is_number
365 $is_a_number = $thing->is_number;
367 Returns true if $thing is a number as understood by Perl.
369 12.34->is_number; # true
371 "12.34"->is_number; # also true
372 is_positive
374 $is_positive = $thing->is_positive;
376 Returns true if $thing is a positive number.
378 0 is not positive.
380 is_negative
382 $is_negative = $thing->is_negative;
384 Returns true if $thing is a negative number.
386 0 is not negative.
388 is_integer
390 $is_an_integer = $thing->is_integer;
392 Returns true if $thing is an integer.
394 12->is_integer; # true
396 12.34->is_integer; # false
397 is_int
399 A synonym for is_integer.
401 is_decimal
403 $is_a_decimal_number = $thing->is_decimal;
405 Returns true if $thing is a decimal number.
407 12->is_decimal; # false
409 12.34->is_decimal; # true
410 ".34"->is_decimal; # true
411 Reference Related Methods
413 The following core functions are implemented.
415 tie, tied, ref, vec.
417 "tie", "tied", and "undef" don't work on code references.
419 Array Methods
421 Array methods work on both arrays and array references:
423 my $arr = [ 1 .. 10 ];
425 $arr->undef;
426 Or:
428 my @arr = ( 1 .. 10 );
430 @arr->undef;
431 List context forces methods to return a list:
433 my @arr = ( 1 .. 10 );
435 print join ' -- ', @arr->grep(sub { $_ > 3 }), "\n";
436 Likewise, scalar context forces methods to return an array reference.
438 As scalar context forces methods to return a reference, methods may be
440 chained
441 my @arr = ( 1 .. 10 );
443 @arr->grep(sub { $_ > 3 })->min->say; # "4\n";
444 These built-in functions are defined as methods:
446 pop, push, shift, unshift, delete, undef, exists, bless, tie, tied,
448 ref, grep, map, join, reverse, and sort, each.
449 As well as:
451 vdelete
453 Deletes a specified value from the array.
455 $a = 1->to(10);
457 $a->vdelete(3); # deletes 3
458 $a->vdelete(2)->say; # "1 4 5 6 7 8 9 10\n"
459 uniq
461 Removes all duplicate elements from an array and returns the new array
463 with no duplicates.
464 my @array = qw( 1 1 2 3 3 6 6 );
466 @return = @array->uniq; # @return : 1 2 3 6
467 first
469 Returns the first element of an array for which a callback returns
471 true:
472 $arr->first(sub { qr/5/ });
474 max
476 Returns the largest numerical value in the array.
478 $a = 1->to(10);
480 $a->max; # 10
481 min
483 Returns the smallest numerical value in the array.
485 $a = 1->to(10);
487 $a->min; # 1
488 mean
490 Returns the mean of elements of an array.
492 $a = 1->to(10);
494 $a->mean; # 55/10
495 var
497 Returns the variance of the elements of an array.
499 $a = 1->to(10);
501 $a->var; # 33/4
502 svar
504 Returns the standard variance.
506 $a = 1->to(10);
508 $a->svar; # 55/6
509 at
511 Returns the element at a specified index. This function does not modify
513 the original array.
514 $a = 1->to(10);
516 $a->at(2); # 3
517 size, elems, length
519 "size", "elems" and "length" all return the number of elements in an
521 array.
522 my @array = qw(foo bar baz);
524 @array->size; # 3
525 elements, flatten
527 my @copy_of_array = $array->flatten;
529 Returns the elements of an array ref as an array. This is the same as
531 "@{$array}".
532 Arrays can be iterated on using "for" and "foreach". Both take a code
534 reference as the body of the for statement.
535 foreach
537 @array->foreach(\&code);
539 Calls &code on each element of the @array in order. &code gets the
541 element as its argument.
542 @array->foreach(sub { print $_[0] }); # print each element of the array
544 for
546 @array->for(\&code);
548 Like foreach, but &code is called with the index, the value and the
550 array itself.
551 my $arr = [ 1 .. 10 ];
553 $arr->for(sub {
554 my($idx, $value) = @_;
555 print "Value #$idx is $value\n";
556 });
557 sum
559 my $sum = @array->sum;
561 Adds together all the elements of the array.
563 count
565 Returns the number of elements in array that are "eq" to a specified
567 value:
568 my @array = qw/one two two three three three/;
570 my $num = @array->count('three'); # returns 3
571 to, upto, downto
573 "to", "upto", and "downto" create array references:
575 1->to(5); # creates [1, 2, 3, 4, 5]
577 1->upto(5); # creates [1, 2, 3, 4, 5]
578 5->downto(5); # creates [5, 4, 3, 2, 1]
579 Those wrap the ".." operator.
581 Note while working with negative numbers you need to use () so as to
583 avoid the wrong evaluation.
584 my $range = 10->to(1); # this works
586 my $range = -10->to(10); # wrong, interpreted as -( 10->to(10) )
587 my $range = (-10)->to(10); # this works
588 head
590 Returns the first element from @list. This differs from shift in that
592 it does not change the array.
593 my $first = @list->head;
595 tail
597 Returns all but the first element from @list.
599 my @list = qw(foo bar baz quux);
601 my @rest = @list->tail; # [ 'bar', 'baz', 'quux' ]
602 Optionally, you can pass a number as argument to ask for the last $n
604 elements:
605 @rest = @list->tail(2); # [ 'baz', 'quux' ]
607 slice
609 Returns a list containing the elements from @list at the indices
611 @indices. In scalar context, returns an array reference.
612 # Return $list[1], $list[2], $list[4] and $list[8].
614 my @sublist = @list->slice(1,2,4,8);
615 range
617 "range" returns a list containing the elements from @list with indices
619 ranging from $lower_idx to $upper_idx. It returns an array reference in
620 scalar context.
621 my @sublist = @list->range( $lower_idx, $upper_idx );
623 last_index
625 my $index = @array->last_index(qr/.../);
627 Returns the highest index whose element matches the given regular
629 expression.
630 my $index = @array->last_index(\&filter);
632 Returns the highest index for an element on which the filter returns
634 true. The &filter is passed in each value of the @array.
635 my @things = qw(pear poll potato tomato);
637 my $last_p = @things->last_index(qr/^p/); # 2
638 Called with no arguments, it corresponds to $#array giving the highest
640 index of the array.
641 my $index = @array->last_index;
643 first_index
645 Works just like last_index but it will return the index of the first
647 matching element.
648 my $first_index = @array->first_index; # 0
650 my @things = qw(pear poll potato tomato);
652 my $last_p = @things->first_index(qr/^t/); # 3
653 at
655 my $value = $array->at($index);
657 Equivalent to "$array->[$index]".
659 Hash Methods
661 Hash methods work on both hashes and hash references.
663 The built in functions work as normal:
665 delete, exists, keys, values, bless, tie, tied, ref, undef,
667 at, get
669 my @values = %hash->get(@keys);
671 Returns the @values of @keys.
673 put
675 %hash->put(%other_hash);
677 Overlays %other_hash on top of %hash.
679 my $h = {a => 1, b => 2};
681 $h->put(b => 99, c => 3); # (a => 1, b => 99, c => 3)
682 set
684 Synonym for put.
686 each
688 Like "foreach" but for hash references. For each key in the hash, the
690 code reference is invoked with the key and the corresponding value as
691 arguments:
692 my $hashref = { foo => 10, bar => 20, baz => 30, quux => 40 };
694 $hashref->each(sub { print $_[0], ' is ', $_[1], "\n" });
695 Or:
697 my %hash = ( foo => 10, bar => 20, baz => 30, quux => 40 );
699 %hash->each(sub { print $_[0], ' is ', $_[1], "\n" });
700 Unlike regular "each", this each will always iterate through the entire
702 hash.
703 Hash keys appear in random order that varies from run to run (this is
705 intentional, to avoid calculated attacks designed to trigger
706 algorithmic worst case scenario in "perl"'s hash tables).
707 You can get a sorted "foreach" by combining "keys", "sort", and
709 "foreach":
710 %hash->keys->sort->foreach(sub {
712 print $_[0], ' is ', $hash{$_[0]}, "\n";
713 });
714 lock_keys
716 %hash->lock_keys;
718 Works as "lock_keys" in Hash::Util. No more keys may be added to the
720 hash.
721 slice
723 Takes a list of hash keys and returns the corresponding values e.g.
725 my %hash = (
727 one => 'two',
728 three => 'four',
729 five => 'six'
730 );
731 print %hash->slice(qw(one five))->join(' and '); # prints "two and six"
733 flip
735 Exchanges values for keys in a hash:
737 my %things = ( foo => 1, bar => 2, baz => 5 );
739 my %flipped = %things->flip; # { 1 => foo, 2 => bar, 5 => baz }
740 If there is more than one occurrence of a certain value, any one of the
742 keys may end up as the value. This is because of the random ordering
743 of hash keys.
744 # Could be { 1 => foo }, { 1 => bar }, or { 1 => baz }
746 { foo => 1, bar => 1, baz => 1 }->flip;
747 Because references cannot usefully be keys, it will not work where the
749 values are references.
750 { foo => [ 'bar', 'baz' ] }->flip; # dies
752 flatten
754 my %hash = $hash_ref->flatten;
756 Dereferences a hash reference.
758 Code Methods
760 Methods which work on code references.
762 These are simple wrappers around the Perl core functions. bless, ref,
764 Due to Perl's precedence rules, some autoboxed literals may need to be
766 parenthesized. For instance, this works:
767 my $curried = sub { ... }->curry();
769 This does not:
771 my $curried = \&foo->curry();
773 The solution is to wrap the reference in parentheses:
775 my $curried = (\&foo)->curry();
777 curry
779 my $curried_code = $code->curry(5);
781 Currying takes a code reference and provides the same code, but with
783 the first argument filled in.
784 my $greet_world = sub {
786 my($greeting, $place) = @_;
787 return "$greeting, $place!";
788 };
789 print $greet_world->("Hello", "world"); # "Hello, world!"
790 my $howdy_world = $greet_world->curry("Howdy");
792 print $howdy_world->("Texas"); # "Howdy, Texas!"
793 What's Missing?
795 • File and socket operations are already implemented in an object-
796 oriented fashion care of IO::Handle, IO::Socket::INET, and IO::Any.
797 • Functions listed in the perlfunc headings
799 • "System V interprocess communication functions",
801 • "Fetching user and group info",
803 • "Fetching network info",
805 • "Keywords related to perl modules",
807 • "Functions for processes and process groups",
809 • "Keywords related to scoping",
811 • "Time-related functions",
813 • "Keywords related to the control flow of your perl program",
815 • "Functions for filehandles, files, or directories",
817 • "Input and output functions".
819 • (Most) binary operators
821 These things are likely implemented in an object oriented fashion by
823 other CPAN modules, are keywords and not functions, take no arguments,
824 or don't make sense as part of the string, number, array, hash, or code
825 API.
826 Autoboxing
828 This section quotes four pages from the manuscript of Perl 6 Now: The
829 Core Ideas Illustrated with Perl 5 by Scott Walters. The text appears
830 in the book starting at page 248. This copy lacks the benefit of
831 copyedit - the finished product is of higher quality.
832 A box is an object that contains a primitive variable. Boxes are used
834 to endow primitive types with the capabilities of objects which
835 essential in strongly typed languages but never strictly required in
836 Perl. Programmers might write something like "my $number =
837 Int->new(5)". This is manual boxing. To autobox is to convert a
838 simple type into an object type automatically, or only conceptually.
839 This is done by the language.
840 autoboxing makes a language look to programmers as if everything is an
842 object while the interpreter is free to implement data storage however
843 it pleases. Autoboxing is really making simple types such as numbers,
844 strings, and arrays appear to be objects.
845 "int", "num", "bit", "str", and other types with lower case names, are
847 primitives. They're fast to operate on, and require no more memory to
848 store than the data held strictly requires. "Int", "Num", "Bit",
849 "Str", and other types with an initial capital letter, are objects.
850 These may be subclassed (inherited from) and accept traits, among other
851 things. These objects are provided by the system for the sole purpose
852 of representing primitive types as objects, though this has many
853 ancillary benefits such as making "is" and "has" work. Perl provides
854 "Int" to encapsulate an "int", "Num" to encapsulate a "num", "Bit" to
855 encapsulate a "bit", and so on. As Perl's implementations of hashes
856 and dynamically expandable arrays store any type, not just objects,
857 Perl programmers almost never are required to box primitive types in
858 objects. Perl's power makes this feature less essential than it is in
859 other languages.
860 autoboxing makes primitive objects and they're boxed versions
862 equivalent. An "int" may be used as an "Int" with no constructor call,
863 no passing, nothing. This applies to constants too, not just
864 variables. This is a more Perl 6 way of doing things.
865 # Perl 6 - autoboxing associates classes with primitives types:
867 print 4.sqrt, "\n";
869 print [ 1 .. 20 ].elems, "\n";
871 The language is free to implement data storage however it wishes but
873 the programmer sees the variables as objects.
874 Expressions using autoboxing read somewhat like Latin suffixes. In the
876 autoboxing mind-set, you might not say that something is "made more
877 mnemonic", but has been "mnemonicified".
878 Autoboxing may be mixed with normal function calls. In the case where
880 the methods are available as functions and the functions are available
881 as methods, it is only a matter of personal taste how the expression
882 should be written:
883 # Calling methods on numbers and strings, these three lines are equivalent
885 # Perl 6
886 print sqrt 4;
888 print 4.sqrt;
889 4.sqrt.print;
890 The first of these three equivalents assumes that a global "sqrt()"
892 function exists. This first example would fail to operate if this
893 global function were removed and only a method in the "Num" package was
894 left.
895 Perl 5 had the beginnings of autoboxing with filehandles:
897 use IO::Handle;
899 open my $file, '<', 'file.txt' or die $!;
900 $file->read(my $data, -s $file);
901 Here, "read" is a method on a filehandle we opened but never blessed.
903 This lets us say things like "$file->print(...)" rather than the often
904 ambagious "print $file ...".
905 To many people, much of the time, it makes more conceptual sense as
907 well.
908 Reasons to Box Primitive Types
910 What good is all of this?
912 • Makes conceptual sense to programmers used to object interfaces as
914 the way to perform options.
915 • Alternative idiom. Doesn't require the programmer to write or read
917 expressions with complex precedence rules or strange operators.
918 • Many times that parenthesis would otherwise have to span a large
920 expression, the expression may be rewritten such that the
921 parenthesis span only a few primitive types.
922 • Code may often be written with fewer temporary variables.
924 • Autoboxing provides the benefits of boxed types without the memory
926 bloat of actually using objects to represent primitives. Autoboxing
927 "fakes it".
928 • Strings, numbers, arrays, hashes, and so on, each have their own
930 API. Documentation for an "exists" method for arrays doesn't have
931 to explain how hashes are handled and vice versa.
932 • Perl tries to accommodate the notion that the "subject" of a
934 statement should be the first thing on the line, and autoboxing
935 furthers this agenda.
936 Perl is an idiomatic language and this is an important idiom.
938 Subject First: An Aside
940 Perl's design philosophy promotes the idea that the language should be
942 flexible enough to allow programmers to place the subject of a
943 statement first. For example, "die $! unless read $file, 60" looks
944 like the primary purpose of the statement is to "die".
945 While that might be the programmers primary goal, when it isn't, the
947 programmer can communicate his real primary intention to programmers by
948 reversing the order of clauses while keeping the exact same logic:
949 "read $file, 60 or die $!".
950 Autoboxing is another way of putting the subject first.
952 Nouns make good subjects, and in programming, variables, constants, and
954 object names are the nouns. Function and method names are verbs.
955 "$noun->verb()" focuses the readers attention on the thing being acted
956 on rather than the action being performed. Compare to "$verb($noun)".
957 Autoboxing and Method Results
959 Let's look at some examples of ways an expression could be written.
961 # Various ways to do the same thing:
963 print(reverse(sort(keys(%hash)))); # Perl 5 - pathological parenthetic
965 print reverse sort keys %hash; # Perl 5 - no unneeded parenthesis
966 print(reverse(sort(%hash,keys)))); # Perl 6 - pathological
968 print reverse sort %hash.keys; # Perl 6 - no unneeded parenthesis
969 %hash.keys ==> sort ==> reverse ==> print; # Perl 6 - pipeline operator
971 %hash.keys.sort.reverse.print; # Perl 6 - autobox
973 %hash->keys->sort->reverse->print; # Perl 5 - autobox
975 This section deals with the last two of these equivalents. These are
977 method calls
978 use autobox::Core;
980 use Perl6::Contexts;
981 my %hash = (foo => 'bar', baz => 'quux');
983 %hash->keys->sort->reverse->print; # Perl 5 - autobox
985 # prints "foo baz"
987 Each method call returns an array reference, in this example. Another
989 method call is immediately performed on this value. This feeding of
990 the next method call with the result of the previous call is the common
991 mode of use of autoboxing. Providing no other arguments to the method
992 calls, however, is not common.
993 "Perl6::Contexts" recognizes object context as provided by "->" and
995 coerces %hash and @array into references, suitable for use with
996 "autobox". (Note that "autobox" also does this automatically as of
997 version 2.40.)
998 "autobox" associates primitive types, such as references of various
1000 sorts, with classes. "autobox::Core" throws into those classes methods
1001 wrapping Perl's built-in functions. In the interest of full
1002 disclosure, "Perl6::Contexts" and "autobox::Core" are my creations.
1003 Autobox to Simplify Expressions
1005 One of my pet peeves in programming is parenthesis that span large
1007 expression. It seems like about the time I'm getting ready to close
1008 the parenthesis I opened on the other side of the line, I realize that
1009 I've forgotten something, and I have to arrow back over or grab the
1010 mouse.
1011 When the expression is too long to fit on a single line, it gets broken
1013 up, then I must decide how to indent it if it grows to 3 or more lines.
1014 # Perl 5 - a somewhat complex expression
1016 print join("\n", map { CGI::param($_) } @cgi_vars), "\n";
1018 # Perl 5 - again, using autobox:
1019 @cgi_vars->map(sub { CGI::param($_[0]) })->join("\n")->concat("\n")->print;
1021 The autoboxed version isn't shorter, but it reads from left to right,
1023 and the parenthesis from the "join()" don't span nearly as many
1024 characters. The complex expression serving as the value being
1025 "join()"ed in the non-autoboxed version becomes, in the autoboxed
1026 version, a value to call the "join()" method on.
1027 This "print" statement takes a list of CGI parameter names, reads the
1029 values for each parameter, joins them together with newlines, and
1030 prints them with a newline after the last one.
1031 Pretending that this expression were much larger and it had to be
1033 broken to span several lines, or pretending that comments are to be
1034 placed after each part of the expression, you might reformat it as
1035 such:
1036 @cgi_vars->map(sub { CGI::param($_[0]) }) # turn CGI arg names into values
1038 ->join("\n") # join with newlines
1039 ->concat("\n") # give it a trailing newline
1040 ->print; # print them all out
1041 Here ends the text quoted from the Perl 6 Now manuscript.
1043
1045 Yes. Report them to the author, scott@slowass.net, or post them to
1046 GitHub's bug tracker at
1047 <https://github.com/scrottie/autobox-Core/issues>.
1048 The API is not yet stable -- Perl 6-ish things and local extensions are
1050 still being renamed.
1051
1053 See the Changes file.
1054
1056 Copyright (C) 2009, 2010, 2011 by Scott Walters and various
1057 contributors listed (and unlisted) below.
1058 This library is free software; you can redistribute it and/or modify it
1060 under the same terms as Perl itself, either Perl version 5.8.9 or, at
1061 your option, any later version of Perl 5 you may have available.
1062 This library is distributed in the hope that it will be useful, but
1064 without any warranty; without even the implied warranty of
1065 merchantability or fitness for a particular purpose.
1066
1068 autobox
1069 Moose::Autobox
1070 Perl6::Contexts
1071 <http://github.com/gitpan/autobox-Core>
1072 IO::Any
1073 Perl 6: <http://dev.perl.org/perl6/apocalypse/>.
1074
1076 Scott Walters, scott@slowass.net.
1077 Tomasz Konojacki has been assisting with maint.
1079 Jacinta Richardson improved documentation and tidied up the interface.
1081 Michael Schwern and the perl5i contributors for tests, code, and
1083 feedback.
1084 JJ contributed a "strip" method for scalars - thanks JJ!
1086 Ricardo SIGNES contributed patches.
1088 Thanks to Matt Spear, who contributed tests and definitions for numeric
1090 operations.
1091 Mitchell N Charity reported a bug and sent a fix.
1093 Thanks to chocolateboy for autobox and for the encouragement.
1095 Thanks to Bruno Vecchi for bug fixes and many, many new tests going
1097 into version 0.8.
1098 Thanks to <http://github.com/daxim> daxim/Lars DIECKOW pushing in fixes
1100 and patches from the RT queue along with fixes to build and additional
1101 doc examples.
1102 Thanks to Johan Lindstrom for bug reports.
1104 Thanks to everyone else who sent fixes or suggestions -- apologies if I
1106 failed to include you here!
1107perl v5.34.0 2022-01-21 autobox::Core(3)