On Mon, Dec 21, 2009 at 7:18 PM, jim <jim.d...@gmail.com> wrote:
> Just posted a short piece on why monads are useful. This was prompted
> by some conversations last week with some folks. Comments, questions
> and criticisms welcome.
>
> http://intensivesystems.net/tutorials/why_monads.html
Thanks for writing that up. I keep reading approachable tidbits
about monads like this, without really digging into learning all
there is to know about monads. It's hardly fair of me to comment
on this at all before I do that deeper digging, but for what it's
worth here's a non-monadic solution to the particular problem
presented. It's just a high-level function that defines
a comp-like fn with the desired behavior:
(defn maybe-comp [& fns]
(fn [x] (reduce #(when %1 (%2 %1)) x (reverse fns))))
Use it like this:
(def all (maybe-comp dec-m double-m inc-m))
It's interesting to me that the definition of maybe-comp above is
arguably simpler that the definition of maybe-m, even without
counting the machinery of 'defmonad'. Presumably this is a hint
to how much more powerful maybe-m is than maybe-comp, and simply
shows I don't yet understand the power of monads.
--Chouser
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