i'm trying to sort the assignment concept out in my mind. as i understand it so far, <- is for IO so you can do something like someIOVar <- readFile filename this will be of type IO String which is different from String as in let someStrVar = "this is a string" to work with an IO String you need to convert it into a String which seems to automatically happen inside a do structure as in: main = do tmplX <- readFile "zztmpl.htm" navbx <- readFile "zznavb.htm" let page = U.replace tmplX "NAVX" navbx are there some other ways to make IO String into String? also, it seems that assignment is different for the '=' in a program vs ghci for functions: sum x y = x + y (program) vs let sum x y = x + y (ghci) but not for strings and other things because you must always preface assignment of values with 'let': let a = 4 i suppose the let is there for variable assignments because such things necessitate a change of state and i've read that this is not desirable in functional programming - you have to work a little harder to do assignment than languages which just allow a = 4 b = 5 c = 6 etc in haskell, is it preferable to do something like this: var <- readFile fn someFunction var or someFunction (readFile fn) -- In friendship, prad ... with you on your journey Towards Freedom http://www.towardsfreedom.com (website) Information, Inspiration, Imagination - truly a site for soaring I's