On Saturday 25 December 2010 00:32:38, Aaron Gray wrote:
> Okay great, works this end too, but what does the 'flip' do ???

It flips the order of arguments to calc. You could also write

main = getContents >>= print . (`calc` []) . lexer

Generally,

flip f = \x y -> f y x

or

flip f x = \y -> f y x

flip f x y = f y x