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Comment by voxcogitatio | Hacker News Reader

I've seen an interesting way to do method chaining in haskell: The '$' operator: Basically it's a low-priority right-associative binary operator that applies the function to the left to everything to the right.

Using the example from the article, one could do it as:

sort -n $ uniq -n $ sort $ awk '{ print $5}' $ grep tcp $ netstat -n

I.e essentially the same but in reverse order.

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($) helps to avoid some parens. The (.) is more common to change functions, and closely related. ($) does not really compose functions, it is function application and right associative.

Your example would rather read something close to

  sort -n . uniq -n . sort . awk '{ print $5}' . grep tcp . netstat -n

(And `$ argument' at the end, if there was one.)

($) is actually the least interesting operator in the world :) But as you say, its parsing precedence makes it useful (because it lets you skip parens).

What I like is how ($) generalises to (<$>) for applicative functors, so you can write

   succ $ 5                -- -> 6
   succ <$> Nothing        -- -> Nothing
   succ <$> Just 5         -- -> Just 6
   succ <$> [1, 2, 3]      -- -> [2, 3, 4]

Who needs "for" loops? :)

I agree. Though I'd say id or const or even less interesting than ($).

(`to change functions' should have been `to chain functions'.)

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