unique-permutations ( ... seq i n quot: ( ... elt -- ... ) -- ... )

Vocabulary

math.combinatorics.private

Inputs

seq	an object
i	an object
n	an object
quot	a quotation with stack effect ( ... elt -- ... )

Outputs

None

Definition

USING: kernel math ranges sequences sequences.private ;

IN: math.combinatorics.private

:: unique-permutations
    ( ... seq i n quot: ( ... elt -- ... ) -- ... )
    i n >=
    [ seq clone quot call ] [
        i n [a..b) [| j |
            i j seq should-swap? [
                i j seq exchange-unsafe seq i 1 +
                n quot unique-permutations
                i j seq exchange-unsafe
            ] when
        ] each
    ] if ; inline recursive