# Set::Array-0.06 by Daniel J. Berger (
[email protected])
NAME
Set::Array - Arrays as objects with lots of handy methods (including Set
comparisons) and support for method chaining.
SYNOPSIS
"my $sao1 = Set::Array->new(1,2,4,"hello",undef);"
"my $sao2 = Set::Array->new(qw(a b c a b c));"
"print $sao1->length; # prints 5"
"$sao2->unique->length->print; # prints 3"
PREREQUISITES
Perl 5.6 or later
The 'Want' module by Robin Houston. Available on CPAN.
DESCRIPTION
Set::Array allows you to create arrays as objects and use OO-style
methods on them. Many convenient methods are provided here that appear
in the FAQ's, the Perl Cookbook or posts from comp.lang.perl.misc. In
addition, there are Set methods with corresponding (overloaded)
operators for the purpose of Set comparison, i.e. +, ==, etc.
The purpose is to provide built-in methods for operations that people
are always asking how to do, and which already exist in languages like
Ruby. This should (hopefully) improve code readability and/or
maintainability. The other advantage to this module is method-chaining
by which any number of methods may be called on a single object in a
single statement.
OBJECT BEHAVIOR
The exact behavior of the methods depends largely on the calling
context.
Here are the rules:
* If a method is called in void context, the object itself is modified.
* If the method called is not the last method in a chain (i.e. it's
called in object context), the object itself is modified by that method
regardless of the 'final' context.
* If a method is called in list or scalar context, a list or list
refererence is returned, respectively. The object itself is NOT
modified.
Here's a quick example:
"my $sao = Set::Array->new(1,2,3,2,3);" "my @uniq = $sao->unique(); #
Object unmodified. '@uniq' contains 3 values." "$sao->unique(); # Object
modified, now contains 3 values"
Here are the exceptions:
* Methods that report a value, such as boolean methods like *exists()*
or other methods such as *at()* or *as_hash()*, never modify the object.
* The methods *clear()*, *delete()*, *delete_at()* and *splice()* will
always modify the object. It seemed much too counterintuitive to call these
methods in any context without actually deleting/clearing the items!
* The methods *shift()* and *pop()* will modify the object AND return
the value that was shifted or popped from the array. Again, it seemed
much too counterintuitive for something like "$val = $sao->shift" to
return a value while leaving the object's list unchanged. If you really
want the first or last value without modifying the object, you can
always use the *first()* or *last()* method, respectively.
* The *join()* method always returns a string and is really meant for
use in conjunction with the *print()* method.
BOOLEAN METHODS
empty() - Returns 1 if the array is empty, 0 otherwise.
exists(*val*) - Returns 1 if *val* exists within the array, 0 otherwise.
STANDARD METHODS
at(*index*) - Returns the item at the given index (or *undef*). A
negative index may be used to count from the end of the array.
clear() - Empties the array (i.e. length becomes 0). You may pass a '1'
to this method to set each element of the array to *undef* rather than
truly empty it.
compact() - Removes undefined elements from the array.
count(*val*) - Returns the number of instances of *val* within the
array.
delete(*val*) - Deletes all items that match *val* from the array.
delete_at(*index, ?index?*) - Deletes the item at the specified index.
If a second index is specified, a range of items is deleted. You may use
-1 or the string 'end' to refer to the last element of the array.
fill(*val,?start?,?length?*) - Sets the selected elements of the array
(which may be the entire array) to *val*. The default value for start is
0. If length is not specified the entire array, however long it may be
at the time of the call, will be filled. Alternatively, a quoted integer
range may be used.
e.g. "$sao->fill('x','3-5');"
The array length/size may not be expanded with this call - it is only
meant to fill in already-existing elements.
first() - Returns the first element of the array (or undef).
flatten() - Causes a one-dimensional flattening of the array,
recursively. That is, for every element that is an array (or hash, or a
ref to either an array or hash), extract its elements into the array.
e.g. "my $sa = Set::Array->new([1,3,2],{one=>'a',two=>'b'},x,y,z);"
"$sao->flatten->join(',')->print; # prints "1,3,2,one,a,two,b,x,y,z""
foreach(*sub ref*) - Iterates over an array, executing the subroutine
for each element in the array. If you wish to modify or otherwise act
directly on the contents of the array, use $_ within your sub reference.
e.g. To increment all elements in the array by one...
"$sao->foreach(sub{ ++$_ });"
$sao->index(*val*) - Returns the index of the first element of the array
object that contains *val*. Returns *undef* if no value is found.
Note that there is no dereferencing here so if you're looking for an
item nested within a ref, use the *flatten* method first.
indices(*val1,?val2?, ?val...?*) - Returns an array consisting of the
elements at the specified indices or *undef* if the element is out of
range.
A range may also be used. It must be a quoted string in '0..3' format.
join(*char*) - Joins the individual elements of the list into a single
string with the elements separated by the value of *char*. Useful in
conjunction with the *print()* method.
e.g. "$sao->join(',')->print;"
last() - Returns the last element of the array (or *undef*).
length() - Returns the number of elements within the array.
max() - Returns the maximum value of an array. No effort is made to
check for non-numeric data.
pop() - Removes the last element from the array. Returns the popped
element.
print(*?1?*) - Prints the contents of the array. If a '1' is provided as
an argument, the output will automatically be terminated with a newline.
This also doubles as a 'contents' method, if you just want to make a
copy of the array, e.g. my @copy = $sao->print;
Can be called in void or list context, e.g.
"$sao->print(); # or..." "print "Contents of array are: ",
$sao->print();"
push(*list*) - Adds *list* to the end of the array, where *list* is
either a scalar value or a list. Returns an array or array reference in
list or scalar context, respectively. Note that it does not return the
length in scalar context. Use the *length* method for that.
reverse() - Reverses the order of the contents of the array.
shift() - Shifts the first element of the array and returns the shifted
element.
sort(*?coderef?*) - Sorts the contents of the array in alphabetical order,
or in the order specified by the optional I<coderef>. Use your
standard I<$a> and I<$b> variables within your calling program, e.g:
my $sao = Set::Array->new(
{ name => 'Berger', salary => 20000 },
{ name => 'Berger', salary => 15000 },
{ name => 'Vera', salary => 25000 },
);
my $subref = sub{ $b->{name} cmp $a->{name} || $b->{salary} <=> $a->{salary} };
$sao14->sort($subref)->flatten->join->print(1);
splice(*?offset?,?length?,?list?*) - Splice the array starting at
position *offset* up to *length* elements, and replace them with *list*.
If no list is provided, the elements are deleted.
Returns an array or array reference in list or scalar context, respectively.
Note that this method will always modify the object, regardless of context.
If your goal was to retrieve a range of values without modifying the object,
use the *indices()* method instead.
unique() - Removes/returns non-unique elements from the list.
unshift(*list*) - Prepends a scalar or list to array. Note that this
method returns an array or array reference in list or scalar context,
respectively. It does not return the length of the array in scalar
context. Use the *length* method for that.
ODDBALL METHODS
as_hash() - Returns a hash based on the current array, with each even
numbered element (including 0) serving as the key, and each odd element
serving as the value. This can be switched by using the *key_order*
option and setting it to 'odd', in which case the even values serve as
the values, and the odd elements serve as the keys. The default is
*even*.
Of course, if you don't care about insertion order, you could just as
well do something like, "$sao-"reverse->as_hash;>
Dies if the array contains an odd number of elements. This method does
not actually modify the object itself in any way. It just returns a
plain hash in list context or a hash reference in scalar context. The
reference is not blessed, therefore if this method is called as part of
a chain, it must be the last method called.
randomize() - Randomizes the order of the elements within the array.
rotate(*direction*) - Moves the last item of the list to the front and
shifts all other elements one to the right, or vice-versa, depending on
what you pass as the direction - 'ftol' (first to last) or 'ltof' (last
to first). The default is 'ltof'.
e.g. my $sao = Set::Array->new(1,2,3);
$sao->rotate(); # order is now 3,1,2
$sao->rotate('ftol'); # order is back to 1,2,3
OVERLOADED (COMPARISON) OPERATORS
General Notes
For overloaded operators you may pass a Set::Array object, or just a
normal array reference (blessed or not) in any combination, so long as
one is a Set::Array object. You may use either the operator or the
equivalent method call.
Examples (using the '==' operator or 'is_equal' method):
my $sao1 = Set::Array->new(1,2,3,4,5); my $sao2 =
Set::Array->new(1,2,3,4,5); my $ref1 = [1,2,3,4,5];
if($sao1 == $sao2)... # valid if($sao1 == $ref1)... # valid if($ref1 ==
$sao2)... # valid if($sao1->is_equal($sao2))... # valid
if($sao1->is_equal($ref1))... # valid
All of these operations return either a boolean value (for equality
operators) or an array (in list context) or array reference (in scalar
context).
& or bag - The union of both sets, including duplicates.
- or difference - Returns all elements in the left set that are not in
the right set.
== or is_equal - This tests for equality of the content of the sets,
though ignores order. Thus, comparing (1,2,3) and (3,1,2) will yield a
*true* result.
!= or not_equal - Tests for inequality of the content of the sets.
Again, order is ignored.
* or intersection - Returns all elements that are common to both sets.
% or symmetric_difference - Returns all elements that are in one set or
the other, but not both. Opposite of intersection.
+ or union - Returns the union of both sets. Duplicates excluded.
EXAMPLES
For our examples, I'll create 3 different objects
my $sao1 = Set::Array->new(1,2,3,a,b,c,1,2,3); my $sao2 =
Set::Array->new(1,undef,2,undef,3,undef); my $sao3 =
Set::Array->new(1,2,3,['a','b','c'],{name=>"Dan"});
How do I...
*get the number of unique elements within the array?*
"$sao1->unique()->length();"
*count the number of non-undef elements within the array?*
"$sao2->compact()->length();"
*count the number of unique elements within an array, excluding undef?*
"$sao2->compact()->unique()->length();"
*print a range of indices?*
"$sao1->indices('0..2')->print();"
*test to see if two Set::Array objects are equal?*
"if($sao1 == $sao2){ ... }"
"if($sao1->is_equal($sao2){ ... } # Same thing"
*fill an array with a value, but only if it's not empty?*
"if(!$sao1->empty()){ $sao1->fill('x') }"
*shift an element off the array and return the shifted value?*
"my $val = $sao1->shift())"
*shift an element off the array and return the array?*
"my @array = $sao1->delete_at(0)"
*flatten an array and return a hash based on now-flattened array?, with
odd elements as the key?*
"my %hash = $sao3->flatten()->reverse->as_hash();"
*delete all elements within an array?*
"$sao3->clear();"
"$sao3->splice();"
KNOWN BUGS
There is a bug in the *Want-0.05* module that currently prevents the use
of most of the overloaded operators, though you can still use the
corresponding method names. The equality operators == and != should
work, however.
FUTURE PLANS
Anyone want a built-in 'permute()' method?
I'm always on the lookout for faster algorithms. If you've looked at the
code for a particular method and you know of a faster way, please email
me. Be prepared to backup your claims with benchmarks (and the benchmark
code you used). Tests on more than one operating system are preferable.
No, *map* is not always faster - *foreach* loops usually are.
More flexibility with the sort method and foreach method.
THANKS
Thanks to all the kind (and sometimes grumpy) folks at
comp.lang.perl.misc who helped me with problems and ideas I had.
Thanks also to Robin Houston for the 'Want' module! Where would method
chaining be without it?
AUTHOR
Daniel Berger
[email protected]
Set/Array version 0.01
======================
INSTALLATION
To install this module type the following:
perl Makefile.PL
make
make test
make install
DEPENDENCIES
This module requires these other modules and libraries:
The 'Want' module by Robin Houston.
COPYRIGHT AND LICENCE
Copyright (C) 2001 Daniel J. Berger. All Rights Reserved.
This module is free software. It may be used, redistributed
and/or modified under the same terms as Perl itself.
