HELP: all-subsets
{ $values { "seq" sequence } { "subsets" sequence } }
{ $description
    "Returns all the subsets of a sequence."
}
{ $examples
    { $example
        "USING: combinatorics ;"
        "{ 1 2 3 } all-subsets"
        "{ { } { 1 } { 2 } { 3 } { 1 2 } { 1 3 } { 2 3 } { 1 2 3 } }"
    }
} ;

HELP: selections
{ $values { "seq" sequence } { "n" integer } { "selections" sequence } }
{ $description
    "Returns all the ways to take n (possibly the same) items from the "
    "sequence of items."
} 
{ $examples
    { $example
        "USING: combinatorics ;"
        "{ 1 2 } 2 selections"
        "{ { 1 1 } { 1 2 } { 2 1 } { 2 2 } }"
    }
} ;