> What would be lost by defining Clojure bind operator like this:
>
> (fn m-bind-state [mv f]
> (fn [s]
> (let [[v ss] (mv s)]
> (f v ss))))
>
> Is there more to it than, "Monadic functions must return monadic
> values.
My first thought was that it would be problematic for the "result"
operator, which would have to take two parameters (or at least accept
two parameters, with a default if passed only one)
Perhaps more importantly, the power of the monad abstraction is that
the types of monadic functions and all the operators are similar. ie.
*all* monadic functions, regardless of the monad, have the (haskell)
type a -> M b
This way, you can write a function that works under many different
monads, as long as it uses the generic facilities to return monadic
values. eg. a lifted inc:
(defn m-inc [v]
(m-result (inc v))
which can be used in the state monad as an argument to bind, even
though it doesn't care about the state at all. If you *do* need the
state (add it to the parameter, for example), you would write
(defn add-state [v]
(fn [s]
[(+ v s) s]))
used like ((m-bind (m-result 4) add-state) 10), giving [14 10]
I hope I got this correct... I'm not an expert on all the mathematical
theory behind monads.
--
You received this message because you are subscribed to the Google
Groups "Clojure" group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
