search-sum-of-pair-in-array.hs

import qualified Data.Map as M                                                                                                 
                                                                                                                               
l = [5, 3, 7, 0, 1, 4, 2]                                                                                                      
m = M.fromList [(x,x)| x <- l]                                                                                                 
                                                                                                                               
searchSumInList xs s =                                                                                                         
    let m = M.fromList [(x,x)| x <- xs]                                                                                        
     in foldl fn [] $ zip [0..] l                                                                                              
    where fn acc (i, e) = let t = s - e                                                                                        
                           in case M.lookup t m of                                                                             
                               Just(v) -> if v /= i then (v, e) : acc else acc                                                 
                               _ -> acc