gistfile1.hs

% ghci                                                                                                            
GHCi, version 7.6.1: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Prelude> let n = map show [1..10]
Prelude> let c = \x y -> concat ["(", x, "+", y, ")"]
Prelude> foldl c "0" n
"((((((((((0+1)+2)+3)+4)+5)+6)+7)+8)+9)+10)"
Prelude> foldr c "0" n
"(1+(2+(3+(4+(5+(6+(7+(8+(9+(10+0))))))))))"