ate a vertex from an Int
--   Used i `mod` maxVAsInt if i is out of bounds.
vertex ∷ Int → Vertex
vertex v | isValidVertex v = Vertex v
         | otherwise       = Vertex $ v `mod` maxVAsInt

-- | Creat
vertex ∷ Int → Vertex
vertex v | isValidVertex v = Vertex v
         | otherwise       = Vertex $ v `mod` maxVAsInt
vertex v | isValidVertex v = Vertex v
         | otherwise       = Vertex $ v `mod` maxVAsInt