[r6rs-discuss] Scheme should not be changed to be case sensitive

From: Chris Hanson <cph>
Date: Thu Nov 16 02:42:35 2006

As someone who has quite a bit of "legacy" Scheme code (about half a
million lines), I'm really unhappy about the suggestion that the
language be made case sensitive. This _despite_ the fact that nearly
all of my current work is based on XML and RDF, where case sensitivity
is a bonus.

I'd like to suggest a compromise: R6RS requires implementations to
provide both case-sensitive and case-insensitive interning of symbols,
but provides a notation to specify which is to be used. In the
absence of any such notation, the default would be implementation
specific. This provides for portability of new code, which would be
marked to indicate its preference. It also provides for backwards
compatibility for the large body of older code.

I have two suggestions for a notation. The one I prefer is a pair of
reader tokens #!fold-case and #!no-fold-case which cause the reader to
change its interning mode. (The reader tokens themselves should
probably be case sensitive.) This notation has two advantages: (1)
it's a simple and direct statement of the programmer's intent, and (2)
it allows files with mixed case sensitivity. (Some readers may
disagree that point (2) is an advantage, but I don't want to quibble
about that; point (1) is sufficient.)

An alternative is to bind the notation into the module system somehow.
Since the module system is responsible for providing meaning to the
names in a program, this is not that much of a stretch. An advantage
of this notation is that the module system's structure might help to
minimize the amount of notation required. However I'm reluctant to
bind this functionality into the module system, particularly since
modules aren't yet that well understood.

Whatever is chosen, I _also_ favor the use of |...| syntax to override
the behavior for a single symbol. (And of course I think that foo and
|foo| should be eq.) This syntax has the additional _major_ advantage
that it gives a standard external representation for all symbols.
Received on Thu Nov 16 2006 - 02:42:29 UTC