[Haskell-cafe] Coming up with a better API for Network.Socket.recv

Jonathan Cast jonathanccast at fastmail.fm
Thu Feb 26 17:12:39 EST 2009

On Thu, 2009-02-26 at 22:45 +0100, Johan Tibell wrote:
> Hi all,
> I find it quite inconvenient to use the `recv` function in
> Network.Socket as it throws an exception when reaching EOF and there's
> no way to check whether EOF has been reached before calling `recv`.
> This means that all calls to `recv` needs to be wrapped in an
> exception handler.


  tryJust (guard . isEOFError) $ recv ...

with base-4 or

  tryJust (ioErrors >=> guard . isEOFError) $ recv ...

with base-3, right?

> I've been thinking about changing the version of
> `recv` that's included in the network-bytestring library [1] so it
> behaves differently from the one in the network library. Before I do
> so I thought I should see if we can reach a consensus on what a nicer
> definition of `recv` would look like. My current thinking is that it
> would mimic what C/Python/Java does and return a zero length
> ByteString when EOF is reached.


In the interest of totality.

Also, Prelude.getChar/System.IO.hGetChar should have return type

  IO (Maybe Char)

in the interest of totality.

> I'm also interested in understanding the reasons behind the design of
> the `recv` function in the network library. More generally, I'm
> interested in discussing the pros and cons of the current Haskell I/O
> library design where the different read functions throw EOF exceptions
> and you have to call e.g. hIsEOF before reading from a Handle.
> 1. http://github.com/tibbe/network-bytestring


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