Re: Problems with lposix on win32

[Rici Lake <lua@...>]

On 15-Jan-06, at 7:25 PM, Chris Marrin wrote:

> Since Lua has multiple return values, why not just always return errno 
> as the second return value of each (relevant) call?

Fair enough. In that case, errno() is unnecessary (and not obviously 
implementable on non Posix systems).

POSIX (and Win32) standardize the names of the errno constants; I agree 
that these should be strings (just simple strings, like "ENOENT"; the 
WSA_ prefix can be deleted, for example, so that the names coincide. 
There's a errno translation mechanism in APR which you could 
stealxxxxrepurpose :) in general, I think looking at APR's API is a 
good idea because a lot of people have thought hard about how to make 
an API which is both portable and easy to use.

Just to explain my reasoning:

In order for functions which might be used as iterators to be usable as 
iterators, it is important that they return <false, error>, rather than 
<nil, error>. However, having thought about this a bit, and tried both 
interfaces, I actually remain convinced that being able to access 
errors "after the fact" leads to simpler code. It is certainly possible 
to write:

  for in, errmsg in f:lines() do
    if errmsg then
      -- handle the error
    end
    -- handle the non-error case
  end

but it requires every script to think about the possibility of errors 
in order to avoid a runtime type error (boolean used where a string is 
required.) Maybe that's not a bad thing, but in many cases it is 
actually ok to just let a loop die if an error is encountered. 
Furthermore, errmsg in the above is local to the for loop, which is 
also a trifle awkward.

> I would rather not globalize the discussion into existing 
> functionality. I just want to get some needed functions online ASAP!

Good point. Sorry. I'll try and focus my thoughts about filesystem 
interfaces for some other thread. :)