[clean-list] Some examples about the Directory library
Ronny Wichers Schreur
ronny@cs.kun.nl
Fri, 19 Dec 2003 14:05:11 +0100
Erik Zuurbier writes (to the Clean Discussion list):
>This design is used all the time. See for instance the way
>opening and closing files works.
>
I don't like it there either.
>Not nice but it makes coding (with pattern matching) a little
>easier.
>
So we need pattern guards
# (r, f)
= freadc f
| Nothing <- r
= ...
| Just c <- r
= ... c ...
and an optimisation to make sure that Nothing and Just are not
allocated if efficiency is important.
>Maybe one time Sparkle could help proving that a program
>never inspects a value that could explode. Then you have the
>best of both worlds.
>
This is something that can be expressed in Clean's current type
system, so I'd prefer that.
Cheers,
Ronny Wichers Schreur