Let's unite sets

Any number of sets can be passed (not just two or three).

By BK


my @numericUnion = union{ $_[0] == $_[1] } [1,2,3], [2,3,4], [9]; #ret
+urns ( 1, 2, 3, 4, 9 ) 

my @stringUnion = union{ $_[0] eq $_[1] } [ qw( aaa bbb ccc ) ], [ qw(
+ bbb ccc ddd ) ]; #returns( 'aaa','bbb','ccc','ddd' ) 

 my @unique = union{ $_[0]->isSameNode } [ qw( list of xml nodes ) ], 
+[ qw( othrer list of xml nodes ) ] #unique node list


sub union(&@){
    my $eq = shift;
    @_ == 1 ? @{ $_[0] } :
    union(
        $eq, [
            @{ $_[0] },
            grep &{sub{
                !grep $eq->( $_, $_[0] ), @_[1..$#_]
            }}( $_, @{ $_[0] } ), @{ $_[1] }
        ], @_[2..$#_]
    )
}
[download]

Comment on Let's unite sets Download Code

Replies are listed 'Best First'.
Re: Let's unite sets by jdporter (Paladin) on Mar 28, 2005 at 21:01 UTC
I'm not sure what's going on with your "equals" concept there. Why is that approach better than `sub union { my %h; @h{@$_} = @$_ for @_; values %h }` [download] ???	[reply] [d/l]
Re^2: Let's unite sets by songahji (Friar) on Mar 28, 2005 at 21:06 UTC
Would your union works for objects? `my @unique = union{ $_[0]->isSameNode } [ qw( list of xml nodes ) ], [ qw( other list of xml nodes ) ] #unique node list` [download] Edited by castaway - added code tags	[reply] [d/l]
Re^3: Let's unite sets by tlm (Prior) on Mar 28, 2005 at 22:04 UTC
Certainly. Notice that the hash keys are "stringified objects", which include a memory locations, like this: `% perl -le 'print bless +{}, "Foo"' Foo=HASH(0x814cbb8)` [download] So objects are considered equal only if their "stringifications" match. You still recover the original object from the corresponding hash value. the lowliest monk	[reply] [d/l]
Re^3: Let's unite sets by jdporter (Paladin) on Mar 29, 2005 at 01:33 UTC
It would, and does. I encourage you to try it for yourself. I also encourage you to look at existing modules, such as Set::Object, which generally do a lot more than just union.	[reply]
Re^4: Let's unite sets by songahji (Friar) on Mar 29, 2005 at 21:23 UTC
Re^5: Let's unite sets by jdporter (Paladin) on Mar 29, 2005 at 22:53 UTC
Re^2: Let's unite sets by songahji (Friar) on Mar 31, 2005 at 20:58 UTC
are you sure it's @h{@_} not $h{@_}	[reply]
Re^3: Let's unite sets by jdporter (Paladin) on Mar 31, 2005 at 23:26 UTC
Oh, yes, quite sure. It's called a "hash slice". You can look it up. :-) In a nutshell: Let's say you have an array @a; then doing `@h{@a} = @a;` [download] is the same as doing `for ( @a ) { $h{$_} = $_; }` [download]	[reply] [d/l] [select]
Re^4: Let's unite sets by songahji (Friar) on Apr 05, 2005 at 19:10 UTC