-------------------------------------------------------------------------------
--  $Id: Beside.hs#1 2009/10/01 10:31:09 REDMOND\\satnams $
-------------------------------------------------------------------------------

module Lava.Beside
where

-------------------------------------------------------------------------------
-- 4-Sided Tile Combinators
-------------------------------------------------------------------------------
-- BESIDE
--            d             g
--            |             |
--            ^             ^
--          -----         -----
--         |     |       |     |
--     b ->|  r  |-> c ->|  s  |-> f
--         |     |       |     |
--          -----         -----
--            |             |
--            ^             ^
--            a             e
-------------------------------------------------------------------------------

beside :: Monad m =>
          (((a, b) -> m (c, d)) ->          -- type of r
          ((e, c)  -> m (f, g)) ->          -- type of s
          (((a,e), b)) -> m (f, (d,g)))     -- type of result
beside r s ((a,e), b)
  = do (c, d) <- r (a, b)
       (f, g) <- s (e, c)
       return  (f, (d,g))
 
-------------------------------------------------------------------------------