                 [ dupd ^^horizontal-add-vector ]
             } cleave
         ]
-        [| src rep | 
+        [| src rep |
             src src rep ^^merge-vector-head :> head
             src src rep ^^merge-vector-tail :> tail
             head tail rep ^^add-vector :> src'

            [ dupd ^^horizontal-add-vector ]
            [ dupd ^^horizontal-add-vector ] tri
        ]
        [| src rep | 
            src src rep ^^merge-vector-head :> head
            src src rep ^^merge-vector-tail :> tail
            head tail rep ^^add-vector :> src'

: ^(sum-vector-2) ( src rep -- dst )
    {
        [ dupd ^^horizontal-add-vector ]
        [| src rep |
            src src rep ^^merge-vector-head :> head
            src src rep ^^merge-vector-tail :> tail
            head tail rep ^^add-vector
