> > > > converting between dotted-decimal strings and a 32-bit network byte orderedAxel Simon wrote:
> > > Does anyone know why these are in the IO monad? Aren't they > pure functions
> > > > binary value?
> >
> > I guess the answer is no for both: The first one can fail
>
That doesn't mean that it should be in the IO monad; using Maybe would suffice.
Agreed. Perhaps I wasn't clear enough in my original question. There appears to be no intrinsic reason why they should be in the IO monad.
> > > > Hence ntoa needs to be an IO action so that the value is read > > immediately before the next ntoa call is executed. > > That shouldn't be an issue so long as the buffer contents are > converted to a Haskell String before the function is called again > within the same thread. > > However, I wouldn't rely upon all implementations of inet_ntoa() being > thread-safe.
> What you could do is to apply unsafePerformIO to
> > [snip] > > Or you could just re-implement the functions in Haskell. > > Apart from the re-entrancy issues with inet_ntoa(), many > implementations of inet_addr() have misfeatures, e.g. allowing octets > to be expressed in octal or hex, or allowing numbers outside of the > 0-255 range (in which case, the top bits overflow into the next > octet).
Perhaps better would be:
inet_addr' :: (Octet,Octet,Octet,Octet) -> HostAddress inet_ntoa' :: HostAddress -> (Octet,Octet,Octet,Octet)
I see Peter Simons has already written something:
http://cryp.to/hsdns/docs/Network.IP.Address.html#v%3Aha2tpl
Dominic.
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