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Everything Your Professor Failed to Tell You About Functional Programming

My Google Alert on Haskell tortured me with weeks of unrelated news about folks called Haskell, sports results from a college of the same name and local incidents from a town of the same name. Finally today I got a on-topic hit. Allow me to share it with you, it is here.

PS Is this is the proper way to submit some interesting link?

By mvw at 2006-01-31 20:55 | LtU Forum | previous forum topic | next forum topic | other blogs | 6739 reads

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PS Is this is the proper way to submit some interesting link?

Sure. That's fine.

People who frequently have news to post should consider becoming contributing editors, which essentially means being able to post to the home page.

By Ehud Lamm at Tue, 2006-01-31 20:59 | login or register to post comments

Nice summary

I quite like that article. I was always baffled by Monads, and the thing that baffled me was, I was expected deep magic but really there isn't much to them. As the article says, they are just a design pattern.

By Noel at Tue, 2006-01-31 22:01 | login or register to post comments

Took Me a While!

It took me a while to grasp that, too. A crucial thing to aid my understanding was the observation that even Haskell doesn't (can't?) enforce the monad laws: the Monad type, do-notation, and related machinery are just conveniences. Once you "get" that a monadic type constructor just returns a higher-order function and the other functions just manipulate those HOFs according to the monad laws, things become a bit clearer. Once you play with monadic implementations in a few different languages (Scheme, O'Caml, even C++...) things become clearer still.

Of course, the joker in the deck, as I've written before, is that, at least for me, monads never get any easier to understand than HOFs do, and for a great many programmers, myself included, HOFs themselves carry what feels like an irreducible level of complexity to them. I've been programming in languages in which functions are first-class for over two decades now, and I still find myself learning things about HOFs all the time!

By Paul Snively at Tue, 2006-01-31 22:24 | login or register to post comments

Picking some nits

Once you "get" that a monadic type constructor just returns a higher-order function and the other functions just manipulate those HOFs according to the monad laws, things become a bit clearer.

Where is the higher-order function (specifically: the one that is returned) in the Maybe monad? Also, type constructors return types. (Let's not make monads even more difficult to understand.)

By Vesa Karvonen at Tue, 2006-01-31 23:00 | login or register to post comments