[m-users.] Bug in posix.readdir (fixed)

[Volker Wysk]

Am Montag, den 14.10.2019, 13:43 +1100 schrieb Julien Fischer:
> On Mon, 14 Oct 2019, Volker Wysk wrote:
> 
> > Am Montag, den 14.10.2019, 13:06 +1100 schrieb Zoltan Somogyi:
> > > On Mon, 14 Oct 2019 03:58:18 +0200, Volker Wysk <
> > > post at volker-wysk.de>
> > > wrote:
> > > > Not sure if I understand correctly, but wouldn't it just be one
> > > > level
> > > > of switching:
> > > > 
> > > >     readdir(Dir, Res, !IO),
> > > >     (
> > > >         Res = ok(yes(File)),
> > > > 	...
> > > >     ;
> > > > 	Res = ok(no),
> > > > 	...
> > > >     ;
> > > > 	Res = error(Err),
> > > > 	...
> > > >     )
> > > 
> > > That is actually two levels of switching: first ok vs error, then
> > > (in the ok case) yes vs no. The fact that you can flatten that
> > > out
> > > in the surface syntax does not change the fact that the generated
> > > code does two nested switches.
> > 
> > Okay. But would that be a bad thing? (I'm just wondering.)
> 
> "Bad" may be too strong a word.  IMO, the nested type is less
> desirable
> because:
> 
> 1. the two-level switch is more expensive.  The flat version
> just needs to switch on the primary tag.

That wouldn't carry weight, when calling readdir.

> 
> 2. "ok(no)" is less meaningful indication of end-of-file (end-of-
> stream)
> than a purpose specific functor like eof.

Okay, this I can understand.

> 
> 3. As a I mentioned elsewhere, it's less consistent with how this
> situation is treated by the stdlib etc.

This too.

Bye
V.W.