Another alternative for doing this with a regexp is also quite bad: 

    /\bd4\b.*\bb2\b|\bb2\b.*\bd4\b/

[download]

But it gets really bad if you are looking for more than two members. Let's say we want to match "sets" containing all of c3, d4, and e5: 

    /\bc3\b.*(\bd4\b.*\be5\b|\be5\b.*\bd4\b)
    |\bd4\b.*(\bc3\b.*\be5\b|\be5\b.*\bc3\b)
    |\be5\b.*(\bc3\b.*\bd4\b|\bd4\b.*\bc3\b)/x

[download]

This gets so bad so fast that I won't even attempt to automate the generation of these regexen for matching larger numbers of elements [though it wouldn't be hard ;> ].

If you know that these sets never have duplicates, then a fairly simple regex has hopes of working and being not horribly slow: 

    my $want= qr/\b(?:c3|d4|e5)\b/;
    my $match= qr/$want.*?$want.*?$want/;

[download]

So $want matches any member that is one of the members that we want while $match matches a set that contains 3 members that we want. If sets contain no duplicates and we want 3 (unique) members, then $match matches what we want. If use ".*?" because I think it will be faster. YMMV.

        - tye (but my friends call me "Tye")

In reply to Re: Set theory in regexs by tye
in thread Set theory in regexs by dcorbin

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