In scheme, I can implement my co-routine by defining a function like this:
(define (spawn prog)
(call/cc
(lambda (start)
(let ((suspend (lambda ()
(call/cc
(lambda (k)
(start k))))))
(prog suspend)))))
Recently I use Frege to program android, I notice that Control.Monad.Cont
is not available, I try to define it follow the book
https://en.wikibooks.org/wiki/Haskell/Continuation_passing_style
newtype Cont r a = Cont { runCont :: ((a -> r) -> r) } -- r is the final result
type of the whole computation
instance Monad (Cont r) where
return a = Cont $ \k -> k a -- i.e. return a =
\k -> k a
(Cont c) >>= f = Cont $ \k -> c (\a -> runCont (f a) k) -- i.e. c >>= f =
\k -> c (\a -> f a k)
But no luck, 'newtype' is not supported by Frege
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