data Symbol = A | B | C | D
              deriving(Eq,Ord,Show)

type SymTuple4 = (Symbol, Symbol, Symbol, Symbol)

perm1 :: SymTuple4 -> SymTuple4
perm1 (a,b,c,d) = (b,a,c,d)

perm2 :: SymTuple4 -> SymTuple4
perm2 (a,b,c,d) = (c,b,a,d)

perm3 :: SymTuple4 -> SymTuple4
perm3 (a,b,c,d) = (d,b,c,a)