prad
i'm using them right i think because it works, but my understanding is fuzzy.
it seems <- is used when you do things like load a file or get arguments from outside or if you are return something from a function
these seem to take the form of something other than an internal type like Int or String and have to be 'massaged' into use with things like show or fromSql etc
the = is used with let and seems to work for any assignments that are internal.
are these assessments correct?
No. You are mixing up monadic computations with normal Haskell functions. First of all using "=" you make an equation. You are not saving a result, you are just saying that two things are the same. You use this to define values and functions: (age, sex, location) = (25, Male, "Germany") fourthRoot = sqrt . sqrt You could just as well write '25' whereever your write 'age'. And you could just as well write 'sqrt . sqrt' whereever you write 'fourthRoot', because you defined them to be the same thing. The '<-' syntax on the other hand is unrelated to functions. You use it to give the result of a monadic computation a name. Example: line <- getLine getLine is a value of type IO String. Notice that getLine is /not/ a function. It's simply a value. But it's a monadic one, because IO is a monad, so whenever you use 'do' notation, you can refer to the result of it by using the '<-' syntax. Let's go deeper into it: content <- readFile "blah.txt" Now readFile is a function. It's of the following type: readFile :: FilePath -> IO String Because it is a function you need to apply it to a value of type FilePath first, yielding, guess what, a simple value. That value is of type IO String, so it's a monadic value, an IO computation. That computation, when run, has a result. And by using '<-' you give this result the name 'content', so you can refer to it. Again, 'content' is /not/ the result of the readFile function, because that result is a computation of type IO String. Let's see the difference: let readBlahTxt = readFile "blah.txt" content <- readBlahTxt This should show the difference more clearly. Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/