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

module Lava.Below
where

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

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

-------------------------------------------------------------------------------