On the disjoiintness of keywords and symbols, and compatibility...

Gauche used to have keywords disjoint from symbols, noted :foo. It's not conforming rnrs, though, so we switched keywords

to be symbols (to be precise, of a subtype of the symbol type). However, there's a library (gauche keyword), in which

all symbols beginning with ':' are pre-bound to itself.

So you can write:

(import (gauche keyword))

(foo :foo 1 :bar 2)

If you don't want to import (gauche keyword), you can still call keyword-accepting procedure by quoting keywords:

(foo ':foo 1 ':bar 2)

If you want to bind a symbol beginning with ':' and want to use keywords as well:

(import (except (gauche keyword) :foo))

(define :foo "foo")

If you do this, you have to quote :foo if you mean it to be a keyword arguments, but you know what you're doing in

that scope.

On Sun, Jul 21, 2019 at 11:23 AM John Cowan <xxxxxx@ccil.org> wrote:

On Sun, Jul 21, 2019 at 4:52 PM Lassi Kortela <xxxxxx@lassi.io> wrote:

But are the different keyword _objects_ incompatible with each other?

No, not in any implementation I know of. There is also the question of whether keywords are a kind of symbol or are disjoint: in Chicken they were historically a kind of symbol but are now disjoint to prevent people from trying to bind them.

The read syntax is different, but if a SRFI simply specifies that the
implementation must have _some_ syntax for keywords, whether it be foo:
or :foo or #:foo, and uses one of them for illustrative purposes but
implementations are allowed to use the others, would that cause problems?

As Arthur says, that would prevent code compatibility: as he doesn't say, it would also be bad for data portability, because keywords are datums in Lisps (except Racket) that have them.

The trouble with #! flags for this purpose is that they are file-global, making it hard to mix and match snippets. They also don't work well for data (what does `read` assume?)

In short, it's all a big mess.

John Cowan http://vrici.lojban.org/~cowan xxxxxx@ccil.org
When I wrote it I was more than a little febrile with foodpoisoning
from an antique carrot that I foolishly ate out of an illjudged faith
in the benignancy of vegetables. --And Rosta