On 12/31/05, Marc Weber wrote:

Hi.. I'm still struggling with monads ;-)

In the tutorial "All about monads" there is the function getOne used:

getOne:: (Random a) => (a,a) -> State StdGen a getOne bound = do g <-get (x,g')= return $ randomR bounds g put g' return x

In the haskell "Yet another Haskell tutorial" by Hal Daume it is said that do {fp <- e; es}

is translated to: let ok p = do {es} ; ok _ = fail "..." in e >>= ok

Using this rule I was able to expand the first "<-" of getOne: getOne2 :: (Random a) => (a,a) -> State StdGen a getOne2 bounds = let ok g = do (x,g') <- return $ randomR bounds g put g' return x ok _ = fail "asd" in get >>= ok

but I couldn't manage to also expand the second. My attempt is: getOne3 :: (Random a) => (a,a) -> State StdGen a getOne3 bounds = let ok g = do let ok2 (x,g') = do { put g'; return x } -- ok2 _ = fail "2" in (return $ randomR bounds g >>= ok2 ok _ = fail "1" in get >>= ok But I get this compile error in at the line marked by a trailing --: "The last statement in a 'do' construct must be an expression"

Can you help me?

Omit the 'do' in 'do let ok2'. -- Friendly, Lemmih