PROPOSAL: add tryFdSeek to unix

Simon Marlow marlowsd at
Wed Jun 29 21:18:25 CEST 2011

On 29/06/11 20:02, John Lato wrote:
>      > I'd like to propose adding a variant of fdSeek which returns errors
>      > directly instead of throwing an exception.
>      >
>     Why wouldn't you just wrap it in Control.Exception.try instead? And
>     what's
>     so special about seeking that suggests that it needs an alternate entry
>     point?
> (Disclosure: I'm one of the people who requested this originally)
> Wrapping a function like `fdSeek` in a `try` to get a non-exception
> variant is wasteful.  Exceptions are a Haskell layer on top of the more
> fundamental library call, and people who want access to that call
> directly shouldn't have to unwrap extra cruft to do so.  Nor should they
> have to re-implement basic functionality because the library doesn't
> expose it.
> fdSeek just happens to be a current need of mine.  I would hope that
> this approach would be adopted across the board.
>     (In other words, I'm opposed to this proposal.)
>   I'm opposed to exceptions, but there's no way to avoid them because
> the library doesn't expose a direct interface.

I think it would make sense to refactor the unix package into a very 
thin "just the foreign imports" layer, and then the current unix as a 
layer on top of that.

It doesn't make a great deal of sense to do this for just one function, 
though.  It would stick out like a sore thumb in the API.


More information about the Libraries mailing list