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by pjscott 5557 days ago
If you don't know Haskell, and you've never used attoparsec, then I'm not surprised that you don't find that code to be particularly clear or readable. Haskell has a steep learning curve, as I said earlier. This is not a very damning criticism of Haskell's suitability for writing parsing code.

By the way, that long import list is actually just importing some basic stuff from the standard library, and the attoparsec parsing library. One of the persistent minor annoyances of Haskell is writing long lists of module imports.
1 comments
alavrik 5557 days ago
Fair enough. I didn't mean to criticize Haskell. In fact, I'm planning to learn it.

I was just surprised that this code was presented as a good example of Haskell's fit to the parsers domain. It would be interesting to see if my perception of this code changes once I get more familiar with the language.

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pjscott 5557 days ago
Ah, okay, I misunderstood you. Yes, I think your perception of the code will change. In particular, the operators from Control.Applicative (the ones that look especially like line noise) are critical to making heads or tails of it. When I posted that link, I momentarily forgot that they're not obvious. They make sense after you've used them for a little while, though.
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jamii 5557 days ago
I write a lot of ocaml code (for money, even!) and haven't touched haskell for about four years. I still find the haskell version here easier to read. I imagine what's tripping you up is the operator soup. Whilst ugly (one of the things that turned me off haskell) it is a lot easier to read once you are familiar with basic haskell typeclasses (applicative, functor etc). That said, the ocaml version could definitely be a lot nicer. Check out eg

Yojson (search for 'let positive_int') http://forge.ocamlcore.org/scm/browser.php?group_id=153

Mirage (using MPL for zero copy parsing) https://github.com/avsm/mirage/blob/master/lib/net/direct/mp...

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alavrik 5555 days ago
Hi there! I do quite a bit of both OCaml and Erlang.

In fact, I borrowed Yojson's json parser for my project (piqi.org). Also, I'm familiar with MPL. It looks very nice, but from what I heard it is fairly immature. And you definitely can't parse HTTP this way :)

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