Comments for Patterns in Functional Programming

Comment on Lenses are the coalgebras for the costate comonad by The Comonad.Reader » Representing Applicatives

The Comonad.Reader » Representing Applicatives — Thu, 02 May 2013 14:19:27 +0000

[...] And now suppose we take our representable functor in the form s -> a and paired it with an "index" into that function, in the form of a concrete s. Then we'd be able to step that s forward or backwards and navigate around our structure of as. And this is precisely the Store Comonad! And this in turn gives a characterization of the lens laws. [...]

Comment on Functional programming by Quora

Quora — Fri, 02 Mar 2012 01:38:06 +0000

As a self-taught PHP programmer how do I go about finding my bad habits?…

* Read other people’s code. * Find a mentor whose ability and style you look up to. * Use a framework. If this chafes, decide why. Try different frameworks. * Study modelling: Design Patterns. * Study another paradigm—e.g. teach yourself Scheme, Lisp,…

Comment on Comprehensions by jeremygibbons

jeremygibbons — Sat, 21 Jan 2012 17:59:02 +0000

Quite a few people have written about probability distributions as a monad; there are some references in the “Just Do It” paper linked above (ie http://www.cs.ox.ac.uk/publications/publication4877-abstract.html).

Comment on Comprehensions by Eric Macaulay

Eric Macaulay — Sat, 21 Jan 2012 13:32:40 +0000

Having just begun to study probability, I found your little facts concerning probability distributions quite intriguing: can you recommend any sources where one might explore further?

Comment on Comprehensions by Josef

Josef — Fri, 20 Jan 2012 13:31:35 +0000

Fair enough.
Considering just the translation of monad comprehensions I personally prefer the version using (>>=) over the one using join though.

Comment on Comprehensions by jeremygibbons

jeremygibbons — Fri, 20 Jan 2012 10:45:44 +0000

I think it’s generally a matter of taste whether to use concat and join or concatMap and bind; they’re equivalent. But imho, algebras for a monad come out much cleaner with join than with bind.

Comment on Comprehensions by Josef

Josef — Thu, 19 Jan 2012 19:40:11 +0000

I’m a little bit surprised that you don’t mention concatMap and use it in the translation of list comprehensions as it is the (>>=) of the list monad and makes the generalization from lists to monads even clearer.

Comment on Comprehensions by jeremygibbons

jeremygibbons — Thu, 19 Jan 2012 17:00:11 +0000

Oops. Fixed – thanks.

Comment on Comprehensions by bmeph

bmeph — Thu, 19 Jan 2012 16:11:39 +0000

Shouldn’t those bag- and set-using comprehensions’ filter be “odd a,” vice “odd x”?
Or is that an established conventional meaning?
(I Am Not A Mathematician, I just play one on the Internet…)

Comment on Comprehensions by Dan Doel

Dan Doel — Thu, 19 Jan 2012 15:06:17 +0000

Monad comprehensions in Haskell 1.4 used MonadZero for matches, and there was no fail in Monad. However, there was also an extra notion of an unfailable pattern, which allowed the following to not use MonadZero:

[ x + y | (x, y) <- l ]

(x, y) is an unfailable pattern because it can only be refuted by bottom. For Haskell 98, unfailable patterns were removed, but it was deemed unacceptable for the above code to use MonadZero, so fail was added instead, and all Monads were given the ability to have arbitrary matches in a weird compromise.