haskell - Continuation Monad and Asynchronous Responses -

haskell - Continuation Monad and Asynchronous Responses -

assume have 3 synchronous functions info on http (these api calls internally):

lookupuser :: string -> io userid lookupusercity :: userid -> io city lookuplocation :: city -> io location

so, monadic composition lookuplocation <=< lookupusercity <=< lookupuser location of user. but, since each of these calls block, prevent rest of programme running.

apparently, continuations help solve this, can't find real examples of it. think signatures rewritten a -> contt r io b, don't see how accomplish callback-like pattern this. if show me (1) how write transform :: (a -> io b) -> (a -> contt r io b) or (2) link real illustration of doing this, grateful.

continuations pattern of working functions, have nil asynchronicity.

what need forkio or more high level abstractions presented libraries async.

haskell asynchronous continuations