# Set::Array-0.06 by Daniel J. Berger (djberg96@hotmail.com) 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: ", $sao->print();" push(*list*) - Adds *list* to the end of the array, where *list* is either a scalar value or a list. Returns an array or array reference in list or scalar context, respectively. Note that it does not return the length in scalar context. Use the *length* method for that. reverse() - Reverses the order of the contents of the array. shift() - Shifts the first element of the array and returns the shifted element. sort(*?coderef?*) - Sorts the contents of the array in alphabetical order, or in the order specified by the optional I. Use your standard I<$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 djberg96@hotmail.com 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.