Question

What’s the difference? Does seq guarantee more flow conditions?

Answer 1

They aren’t related at all.

seq has the type:

seq :: a -> b -> b

It is used (as seq a b, or a `seq` b) to evaluate a to head normal form, which is a fancy way of saying that it forces the lazy value a to be evaluated a little bit. It has nothing to do with monads.

>>= is for sequencing monads. It has the type:

(>>=) :: Monad m => m a -> (a -> m b) -> m b

It is used to get the value from a monadic value and pass it to a function that returns another monadic value. Basically something like:

getLine >>= putStrLn

which would get a string of input from the command-line and then print it out.

So, basically, no relation at all.