An HTTP client in Haskell using io-streams

http://blogs.operationaldynamics.com/andrew/software/haskell/http-streams-introduction

by dons • 13 years ago

41 16 13 years ago

blogs.operationaldynamics.com

archivator2• 13 years ago

I have to say this looks like a really convenient library!

Aside: As a Haskell beginner, I find it astonishing that 1-letter names are the norm in Haskell-land. To me, names are not just placeholders imposed on you by the language, they should convey meaning, too!

tinco• 13 years ago

They should and they do. But for local variables Haskell programmers generally assert one letter adequately conveys the meaning, especially since you know the type. But the second you can't is also the second you should use more than one letter.

cpa• 13 years ago

It's quite common in Haskell to give 1-letter names to variables that are short lived.

Also, Haskell programmers use 1-letter variable names in functions that could/should be made point free [1] but aren't for some reason [2].

[1] \c -> c + 1 is not point free whereas (+1) is. An expression is point free if it doesn't have any bound variable.

[2] Because reasoning with flip or const may be confusing in the current context for example.

dons• 13 years ago

As always, parametric polymorphism necessitates one-letter names, as variables can really stand for anything at all. The compiler guarantees you can't know much (or anything) about some polymorphic variables.

Other idioms come from math, e.g. 'x' for an unknown value, and then we get 'xs' for a list of unknown values.

    map :: (a -> b) -> [a] -> [b]
    map f (x:xs) = f x : map f xs

Is much clearer than the Zed Shaw version:

    map theFunction (firstElement:otherElements) = theFunction firstElement : map theFunction otherElements

EwanToo• 13 years ago

In the end it's a matter of taste, I find the second version much clearer

archivator2• 13 years ago

I'm aware of polymorphism and the list convention and I'm not going to argue against them.

However, the example code uses `c' for connection and `q' for query. Surely, knowing what those are from the variable name would be a good thing?

It's not that I want to impose Obj-C's verbosity but the other extreme (1-letter names) is just as bad.

gtani• 13 years ago

They're conventions that work because you see them over and over in small functions, the "small functions" being key.

    (go), type parameters, (x:xs) "\ds ->", "import qualified This as That".

I think it's just like a java programmer internalizes when to use HashSet, HashMap, TreeSet, ArrayList etc. After a while you just know what to do.

______________

yesterday's long debate about this:

http://www.reddit.com/r/programming/comments/19mw7v/on_f_rea...

________

APL and C, with some scheme and prolog thrown in, were my first languages, so maybe readability just isn't important to me ;-}

aristidb• 13 years ago

Well, at least the monad abuse uses a real monad, but why not just use lens (http://lens.github.com/)?

dschiptsov• 13 years ago

Look Ma, no sockets?)

mercurial2• 13 years ago

Io-streams looks nice, but I think I'll stay with pipes. Along with pipes-safe, it lets you for instance open resources safely inside your stream, which is a very convenient feature at times.

microtonal• 13 years ago

I like Snap, but I am still skeptic too. One of the nicer things of enumeratee, conduit, and pipes is that you can use them in pure code as well. io-streams drags in the IO monad if you want to structure code as streams, even if your 'enumerator', 'enumeratee' or 'iterator' is pure.

mercurial2• 13 years ago

I think that's a design goal. The idea is to pipe IO streams and not arbitrary streams, which seems to make for a much less complicated machinery (just look at the types signatures from pipes :) ). It's a viable design choice, but it certainly has drawbacks as well.

An HTTP client in Haskell using io-streams

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