[MLton-devel] basis-2002: IO

[Stephen Weeks]

> Looking back at the BinOrTextIO functor, I see that it's very similar to
> what is done in the PolyML sources.  That is, use an imperative buffer,
> but if getInstream is called on the instream, turn it into a
> StreamIO.instream.  We ought to be able to do the same thing here, but
> building on the StreamIO functor to get the remaining functions.
> Unfortunately, my StreamIO isn't as fast as the StreamIO produced by the
> BinOrTextIO functor. 

That's OK with me.  It's not nearly as important (to me) for StreamIO
to be fast.  And, I suspect that with some work the new StreamIO can
be made almost as fast as the old one.

> There are two structures matching the CHAR signature. The Char structure
> provides the extended ASCII 8-bit character set and locale-independent
> operations on them. For this structure, Char.maxOrd = 255.
...
> This is probably archaism in the Basis spec, but Char.char needs to be an
> 8 bit entity.

Once we confirm this is not an error in the spec, we can go ahead and
merge Word8.word and char.  Although I don't see it as very important.

> Again, it depends on what "level" of backwards compatibility we're
> looking for.  I could (easily) create a BASIS_1997 signature and a
> Basis1997 structure that opens Basis2002 and wraps functions whose
> types have changed (Array and Vector functions, OS.FileSys.readDir,
> etc.)

Great.

> That should allow most programs to type-check and compile, but it
> won't take care of functions whose semantics have changed.
> Likewise, we won't be able to recover the non-opaque signature
> matches.  The major semantic change that I've noticed is that
> Time.time admits negative values, so Time.- doesn't raise Time as
> often as it did before.  (In particular, all our problems with
> Time.now () going backwards wouldn't raise an exception, although
> we'd get strange results.)

I don't mind about the non-opaque stuff.  MLton doesn't check it
anyways.  As to Time, we can just leave around both implementations.
And do wrappers every where else.


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