NAME¶
Set::Object - set of objects and strings
SYNOPSIS¶
use Set::Object qw(set);
my $set = set(); # or Set::Object->new()
$set->insert(@thingies);
$set->remove(@thingies);
@items = @$set; # or $set->members for the unsorted array
$union = $set1 + $set2;
$intersection = $set1 * $set2;
$difference = $set1 - $set2;
$symmetric_difference = $set1 % $set2;
print "set1 is a proper subset of set2"
if $set1 < $set2;
print "set1 is a subset of set2"
if $set1 <= $set2;
# common idiom - iterate over any pure Perl structure
use Set::Object qw(reftype);
my @stack = $root;
my $seen = Set::Object->new(@stack);
while (my $object = pop @stack) {
if (reftype $object eq "HASH") {
# do something with hash members
# add the new nodes to the stack
push @stack, grep { ref $_ && $seen->insert($_) }
values %$object;
}
elsif (reftype $object eq "ARRAY") {
# do something with array members
# add the new nodes to the stack
push @stack, grep { ref $_ && $seen->insert($_) }
@$object;
}
elsif (reftype $object =~ /SCALAR|REF/) {
push @stack, $$object
if ref $$object && $seen->insert($$object);
}
}
DESCRIPTION¶
This modules implements a set of objects, that is, an unordered collection of
objects without duplication.
The term
objects is applied loosely - for the sake of Set::Object,
anything that is a reference is considered an object.
Set::Object 1.09 and later includes support for inserting scalars (including the
empty string, but excluding "undef") as well as objects. This can be
thought of as (and is currently implemented as) a degenerate hash that only
has keys and no values. Unlike objects placed into a Set::Object, scalars that
are inserted will be flattened into strings, so will lose any magic (eg, tie)
or other special bits that they went in with; only strings come out.
CONSTRUCTORS¶
Set::Object->new( [ list] )¶
Return a new "Set::Object" containing the elements passed in
list.
"set(@members)"¶
Return a new "Set::Object" filled with @members. You have to
explicitly import this method.
New in Set::Object 1.22: this function is now called as a method to
return new sets the various methods that return a new set, such as
"->intersection", "->union", etc and their
overloaded counterparts. The default method always returns
"Set::Object" objects, preserving previous behaviour and not second
guessing the nature of your derived Set::Object class.
"weak_set()"¶
Return a new "Set::Object::Weak", filled with @members. You have to
explicitly import this method.
INSTANCE METHODS¶
insert( [ list] )¶
Add items to the "Set::Object".
Adding the same object several times is not an error, but any
"Set::Object" will contain at most one occurrence of the same
object.
Returns the number of elements that were actually added. As of Set::Object 1.23,
"undef" will not insert.
includes( [ list] )¶
has( [ list] )¶
contains( [ list] )¶
Return "true" if
all the objects in
list are members of
the "Set::Object".
list may be empty, in which case
"true" is always returned.
As of Set::Object 1.23, "undef" will never appear to be present in any
set (even if the set contains the empty string). Prior to 1.23, there would
have been a run-time warning.
member( [ item] )¶
element( [ item] )¶
Like "includes", but takes a single item to check and returns that
item if the value is found, rather than just a true value.
members¶
elements¶
Return the objects contained in the "Set::Object" in random (hash)
order.
Note that the elements of a "Set::Object" in list context are returned
sorted - @$set - so using the "members" method is faster.
size¶
Return the number of elements in the "Set::Object".
remove( [ list] )¶
delete( [ list] )¶
Remove objects from a "Set::Object".
Removing the same object more than once, or removing an object absent from the
"Set::Object" is not an error.
Returns the number of elements that were actually removed.
As of Set::Object 1.23, removing "undef" is safe (but having an
"undef" in the passed in list does not increase the return value,
because it could never be in the set)
weaken¶
Makes all the references in the set "weak" - that is, they do not
increase the reference count of the object they point to, just like
Scalar::Util's "weaken" function.
This was introduced with Set::Object 1.16, and uses a brand new type of magic.
Use with caution. If you get segfaults when you use "weaken",
please reduce your problem to a test script before submission.
New: as of Set::Object 1.19, you may use the "weak_set"
function to make weak sets, or "Set::Object::Weak->new", or
import the "set" constructor from "Set::Object::Weak"
instead. See Set::Object::Weak for more.
Note to people sub-classing "Set::Object": this
method re-blesses the invocant to "Set::Object::Weak". Override the
method "weak_pkg" in your sub-class to control this behaviour.
is_weak¶
Returns a true value if this set is a weak set.
strengthen¶
Turns a weak set back into a normal one.
Note to people sub-classing "Set::Object": this
method re-blesses the invocant to "Set::Object". Override the method
"strong_pkg" in your sub-class to control this behaviour.
invert( [ list] )¶
For each item in
list, it either removes it or adds it to the set, so
that a change is always made.
Also available as the overloaded operator "/", in which case it
expects another set (or a single scalar element), and returns a new set that
is the original set with all the second set's items inverted.
clear¶
Empty this "Set::Object".
as_string¶
Return a textual Smalltalk-ish representation of the "Set::Object".
Also available as overloaded operator "".
equal( set )¶
Returns a true value if
set contains exactly the same members as the
invocant.
Also available as overloaded operator "==" (or "eq").
not_equal( set )¶
Returns a false value if
set contains exactly the same members as the
invocant.
Also available as overloaded operator "!=" (or "ne").
intersection( [ list] )¶
Return a new "Set::Object" containing the intersection of the
"Set::Object"s passed as arguments.
Also available as overloaded operator "*".
union( [ list] )¶
Return a new "Set::Object" containing the union of the
"Set::Object"s passed as arguments.
Also available as overloaded operator "+".
difference ( set )¶
Return a new "Set::Object" containing the members of the first
(invocant) set with the passed "Set::Object"s' elements removed.
Also available as overloaded operator "-".
unique ( set )¶
symmetric_difference ( set )¶
Return a new "Set::Object" containing the members of all passed sets
(including the invocant), with common elements removed. This will be the
opposite (complement) of the
intersection of the two sets.
Also available as overloaded operator "%".
subset( set )¶
Return "true" if this "Set::Object" is a subset of
set.
Also available as operator "<=".
proper_subset( set )¶
Return "true" if this "Set::Object" is a proper subset of
set Also available as operator "<".
superset( set )¶
Return "true" if this "Set::Object" is a superset of
set. Also available as operator ">=".
proper_superset( set )¶
Return "true" if this "Set::Object" is a proper superset of
set Also available as operator ">".
is_null( set )¶
Returns a true value if this set does not contain any members, that is, if its
size is zero.
Set::Scalar compatibility methods¶
By and large, Set::Object is not and probably never will be feature-compatible
with Set::Scalar; however the following functions are provided anyway.
compare( set )¶
returns one of:
"proper intersect"
"proper subset"
"proper superset"
"equal"
"disjoint"
is_disjoint( set )¶
Returns a true value if the two sets have no common items.
as_string_callback( set )¶
Allows you to define a custom stringify function. This is only a class method.
If you want anything fancier than this, you should sub-class Set::Object.
FUNCTIONS¶
The following functions are defined by the Set::Object XS code for convenience;
they are largely identical to the versions in the Scalar::Util module, but
there are a couple that provide functions not catered to by that module.
Please use the versions in Scalar::Util in preference to these functions. In
fact, if you use these functions in your production code then you may have to
rewrite it some day. They are retained only because they are "mostly
harmless".
- blessed
- Do not use in production code
Returns a true value if the passed reference (RV) is blessed. See also
Acme::Holy.
- reftype
- Do not use in production code
A bit like the perl built-in "ref" function, but returns the
type of reference; ie, if the reference is blessed then it returns
what "ref" would have if it were not blessed. Useful for
"seeing through" blessed references.
- refaddr
- Do not use in production code
Returns the memory address of a scalar. Warning: this is not
guaranteed to be unique for scalars created in a program; memory might get
re-used!
- is_int, is_string, is_double
- Do not use in production code
A quick way of checking the three bits on scalars - IOK (is_int), NOK
(is_double) and POK (is_string). Note that the exact behaviour of when
these bits get set is not defined by the perl API.
This function returns the "p" versions of the macro (SvIOKp, etc);
use with caution.
- is_overloaded
- Do not use in production code
A quick way to check if an object has overload magic on it.
- ish_int
- Deprecated and will be removed in 2014
This function returns true, if the value it is passed looks like it
already is a representation of an integer. This is so that
you can decide whether the value passed is a hash key or an array
index.
- is_key
- Deprecated and will be removed in 2014
This function returns true, if the value it is passed looks more like an
index to a collection than a value of a collection. Similar
to the looks_like_number internal function, but weird. Avoid.
- get_magic
- Do not use in production code
Pass to a scalar, and get the magick wand ("mg_obj") used by the
weak set implementation. The return will be a list of integers which are
pointers to the actual "ISET" structure. Whatever you do don't
change the array :). This is used only by the test suite, and if you find
it useful for something then you should probably conjure up a test suite
and send it to me, otherwise it could get pulled.
CLASS METHODS¶
These class methods are probably only interesting to those sub-classing
"Set::Object".
- strong_pkg
- When a set that was already weak is strengthened using
"->strengthen", it gets re-blessed into this package.
- weak_pkg
- When a set that was NOT already weak is weakened using
"->weaken", it gets re-blessed into this package.
- tie_array_pkg
- When the object is accessed as an array, tie the array into this
package.
- tie_hash_pkg
- When the object is accessed as a hash, tie the hash into this
package.
SERIALIZATION¶
It is possible to serialize "Set::Object" objects via Storable and
duplicate via "dclone"; such support was added in release 1.04. As
of "Set::Object" version 1.15, it is possible to freeze scalar
items, too.
However, the support for freezing scalar items introduced a backwards
incompatibility. Earlier versions than 1.15 will "thaw" sets frozen
using Set::Object 1.15 and later as a set with one item - an array that
contains the actual members.
Additionally, version 1.15 had a bug that meant that it would not detect
"freeze" protocol upgrades, instead reverting to pre-1.15 behaviour.
"Set::Object" 1.16 and above are capable of dealing correctly with all
serialized forms, as well as correctly aborting if a "newer"
"freeze" protocol is detected during "thaw".
The following benchmark compares "Set::Object" with using a hash to
emulate a set-like collection (this is an old benchmark, but still holds
true):
use Set::Object;
package Obj;
sub new { bless { } }
@els = map { Obj->new() } 1..1000;
require Benchmark;
Benchmark::timethese(100, {
'Control' => sub { },
'H insert' => sub { my %h = (); @h{@els} = @els; },
'S insert' => sub { my $s = Set::Object->new(); $s->insert(@els) },
} );
%gh = ();
@gh{@els} = @els;
$gs = Set::Object->new(@els);
$el = $els[33];
Benchmark::timethese(100_000, {
'H lookup' => sub { exists $gh{33} },
'S lookup' => sub { $gs->includes($el) }
} );
On my computer the results are:
Benchmark: timing 100 iterations of Control, H insert, S insert...
Control: 0 secs ( 0.01 usr 0.00 sys = 0.01 cpu)
(warning: too few iterations for a reliable count)
H insert: 68 secs (67.81 usr 0.00 sys = 67.81 cpu)
S insert: 9 secs ( 8.81 usr 0.00 sys = 8.81 cpu)
Benchmark: timing 100000 iterations of H lookup, S lookup...
H lookup: 7 secs ( 7.14 usr 0.00 sys = 7.14 cpu)
S lookup: 6 secs ( 5.94 usr 0.00 sys = 5.94 cpu)
THREAD SAFETY¶
This module is not thread-safe.
AUTHOR¶
Original Set::Object module by Jean-Louis Leroy, <jll@skynet.be>
Set::Scalar compatibility, XS debugging, weak references support courtesy of Sam
Vilain, <samv@cpan.org>.
New maintainer is Reini Urban <rurban@cpan.org>. Patches against
<
https://github.com/rurban/Set-Object/> please. Tickets at RT
<
https://rt.cpan.org/Public/Dist/Display.html?Name=Set-Object>
LICENCE¶
Copyright (c) 1998-1999, Jean-Louis Leroy. All Rights Reserved. This module is
free software. It may be used, redistributed and/or modified under the terms
of the Perl Artistic License
Portions Copyright (c) 2003 - 2005, Sam Vilain. Same license.
Portions Copyright (c) 2006, 2007, Catalyst IT (NZ) Limited. Same license.
Portions Copyright (c) 2013, cPanel. Same license.
SEE ALSO¶
perl(1),
perltie(1), Set::Scalar, overload.pm