M is [0 0 0 0 0 0;
      0 0 1 0 0 0;
      0 1 0 0 0 0;
      0 1 1 1 1 0;
      0 0 0 0 0 0]

gen M
 where gen x is f x (adj x) where (f x y is (x&2=y)|3=y)
 where adj x is +/[r'r x;r'l x;l'r x;l'l x;l'x;r'x;r x;l x]
  where (r is -1!)
  where  l  is 1!

gen M
 where gen x is f x (adj x) where (f x y is (x&2=y)|3=y)
 where adj x is +/[-1!'-1!x;-1!'1!x;1!'-1!x;1!'1!x;1!'x;-1!'x;-1!x;1!x]

\

gen:{(x&2=k)|3=k:+/adj x}
adj:{(r'r@;r'l@;l'r@;l'l@;l';r';r:-1!;l:1!)@\:x}