[r6rs-discuss] Unicode issues

From: Thomas Lord <lord>
Date: Wed, 29 Aug 2007 15:33:44 -0700

William D Clinger wrote:
> In short: We can develop a nice API for immutable texts,
> and make it into a popular SRFI, so long as we have O(1)
> string operations. If some implementations of Scheme were
> to abandon O(1) string operations just so they can use an
> inefficient representation, such as UTF-8 or UTF-16, then
> the texts datatype might perform poorly in those systems,
> but that's okay. Users who care about the performance of
> immutable texts would just avoid those implementations.
>


A small criticism:

I think you confuse the issue when focus on immutable texts
that way. Let's suppose that you have immutable texts for which
string algebra (of substrings and concats) is very fast. Then, instantly,
you also have mutable texts (with but one layer of indirection).

I think a better way to say it might be to say that low-level string
reps should be purely functional. Then you can build "stateful" things
on top of that.

Mutable strings are only one of the things you might build. You could
build strings that have an edit history and an undo facility. And you
could mix in things like character properties or region overlays. And,
lot's of other weird stuff.

Functional strings are definitely the low-level thing to aim for
but that doesn't mean applications wind up seeing only immutable
strings. It's worth, when talking about functional strings, mentioning
that it really gives you not just mutable strings but a rich design space
of different kinds of mutable strings.

-t
Received on Wed Aug 29 2007 - 18:33:44 UTC