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Comment by nine_k | Hacker News Reader

Effects are pretty smoothly described by monads; there's an entire well-respected language built on top of that.

One of the problems of the purely applicative approach is that you get a nice algebra for describing your results, including the sequence of effects, but reasoning about the resources spent by the computation becomes harder.

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monads were certainly a clever fix for the difficulties otherwise caused by passing around the world as a value.

I might argue that laziness makes haskell something different than purely applicative.

It's not just pure values being passed around. It's a language built atop suspended self-caching invocable thunks getting knotted up and then firing off in chain reaction.

    main = do
      let
        hello = foo world
        world = bar hello
      putStrLn $ show hello
      putStrLn $ show world
     where
       foo v = [v]
       bar v = length v

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