interpretation(2, [
    function(c(_), [1,0]),
    function(^(_,_), [
        0,0,
        0,1]),
    function(v(_,_), [
        0,1,
        1,1]),
    function(f(_,_), [
        1,1,
        1,0])]).
% isofilter: input=1, kept=1, checks=0, perms=0, 0.00 seconds.