On 10/12/10 12:39 PM, Gene A wrote:
splitMiddle :: forall a. [a] -> ([a], [a]) splitMiddle = (id &&& (length >>> flip div 2)) >>> (\(xs,a) -> splitAt a xs)
But is that really easier to understand at a glance then splitMiddle xs = splitAt (length xs `div` 2) xs ? It seems to me that while point-free style is nice and I personally us it extensively, sticking to it religiously can sometimes lead to code that is *less* clear. Also, I don't see why one would prefer >>> over the standard function composition operator, ".". Using this and uncurry you could actually make your point-free style definition much more succinct and arguably easier to read: splitMiddle = uncurry splitAt . ((`div` 2) . length &&& id)
OKAY here is where the thoughts can come in to play and are a direct result of the pointfree style that is adopted as a direct result of using arrow notation. [...]
I completely agree with you that point-free style is nice; I am certainly not arguing against it. However, it can be over-kill, and there is no reason that I can see why using the arrow notation ">>>" in place of the standard function notation "." helps one write function in a point-free style.
The other nice use of arrow is INSIDE of a monadic structure:
"Now is the time to come to the aid of our country" >>= (return >>> words >>> concat) "Nowisthetimetocometotheaidofourcountry" [...]
Your use of a monad here both redundant and obfuscatory; a much simpler version of this code is (concat . words) "Now is the time to come to the aid of our country"
squeezeSentenceF :: forall (f :: * -> *). (Functor f) => f [Char] -> f [Char] squeezeSentenceF css = (squeeze <$>) css squeezeSentenceF ["This is how to do a list of sentences", "It makes use of applicatives too"] ["Thisishowtodoalistofsentences","Itmakesuseofapplicativestoo"] [...]
You aren't really using applicative style here, you are just defining a shorthand for calling "fmap squeeze". Also, your function could be expressed in point-free style as follows: squeezeSentenceF = fmap squeeze
I think that the more you mix and match ALL of the tools and do a little experimentation with them, that it then begins to be a situation where your thoughts of how to compose things are not locked down to one way and it opens up your mind to many possibilities. I am a proponent of having and using ALL the available tools in a mix and match way if need be.
I agree, but what I oppose is the choice of fancy tools because they are fancy rather than because they get the job done better than simple tools, because the fancy tools often carry a price with them over the simpler tools. Cheers, Greg