Source code in the v programming language

[comb [m lst] let
   [ [m zero?] [[[]]]
     [lst null?] [[]]
     [true] [m pred lst rest comb [lst first swap cons]  map
            m lst rest comb concat]
   ] when].

[comb
   [ [pop zero?] [pop pop [[]]]
     [null?] [pop pop []]
     [true] [ [m lst : [m pred lst rest comb [lst first swap cons]  map
            m lst rest comb concat]] view i ]
   ] when].

[comb
   [2dup [a b : a b a b] view].
   [2pop pop pop].

   [ [pop zero?] [2pop [[]]]
     [null?] [2pop []]
     [true] [2dup [pred] dip uncons swapd comb [cons] map popd rollup rest comb concat]
   ] when].