solving the word cube in voltron

In response to: http://programmingpraxis.com/2010/07/13/word-cube/

/* returns array of words found in the 9 letters provided */
function solveCube($letters) {
    $words = newType(TFile, 'words.txt')->splitBy("\n");

    return newType(TString, $letters)
        ->asArray
        ->powerSet('contains', $letters[4])
        ->map('permutations', I('asString')->in($words))
        ->map('join');
}

echo solveCube('ncbciune');

There are a few alternative ways that could be written and I am not sure if the idea of just having an optional filter as arguments to powerSet and permutations is entirely intuitive but the reality is that w/o the filter permutations will die on anything over 8 unless you crank the memory up in php.ini and thats just filthy.

Next post I will delve into iterative permutation and powerset internals on Array as that is obviously where the meat of that solution lies.