> On 2 Nov 2017, at 10:10 , Guillermo Polito <guillermopol...@gmail.com> wrote:
>
> My first hunch is that you don't want to change PositionableStream. Because
> it works on collections and files (because of inheritance). But not on other
> kind of streams that are not part of the hierarchy, such as sockets. And we
> are cleaning that part.
>
> Instead, some time ago Sven produced a really nice hierarchy of stream
> decorators. Check the package:
>
> Zinc-Character-Encoding-Core
>
> There you have
>
> ZnBufferedReadStream
>
> That implements buffering in an orthogonal way. Maybe it makes more sense to
> put such method there?
>
I wanted this to be something light-weight. I really don’t want to have to
wrap my stream in a decorator before peeking ahead.
Because I’m doing this in SmaCC, I implemented #explore: (that’s the name I
chose) in SmaCCLineNumberStream. But I think that the general solution is to
put this method in a Trait, so that it can be combined into any stream, whether
or not that stream inherits from PositionableStream. There are probably other
methods that could go in such a trait too.
Actually, the idea of resetting a stream to a prior position is much less
general, and easier to implement, then general positionability. Over the
weekend I posted an issue that discusses positioning a MultiButeFileStream —
that’s a good example.
Here is my implementation — really simple.
```
explore: aBlock
"evaluate aBlock with this stream as argument. When done, reset my
position to the current position."
| savedPosition |
savedPosition := self position.
[ ^ aBlock value: self ] ensure: [ self position: savedPosition ]
```
Andrew
