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usage of various characters '[', ']', and ':'
- To: kawa at sources dot redhat dot com
- Subject: usage of various characters '[', ']', and ':'
- From: Felix S Klock II <pnkfelix at MIT dot EDU>
- Date: Sat, 18 Aug 2001 18:34:57 -0400
I'm trying to figure out what special significance the characters '[',
']', and ':' have in Kawa
Kawa's handling of the colon character seems to violate R5RS, and thus
sticks out like a sore thumb for my work. I can't currently support
handling the ":=" operator in the language I'm parsing because of
Kawa's handling of colon.
Here are some example evaluations:
(quote :=) ==> =:
':=asfda ==> =asfda:
(symbol? '=:) ==> #f
All this of course is probably be considered perfectly valid, given
the description of Keywords in section 7.3 of the Kawa manual. But I
would like a way to treat the colon in an R5RS compliant manner, even
if it were a command-line or environmental option to disable Keywords,
[which I don't use]
Another option (which is probably cleaner, in terms of overall design)
would be to make quotation a higher precedence operation on tokens
than keywordization (in other words, if I say ':asfdasasfsasa, I'm
saying I want a symbol, not a keyword). Quote is a special form
anyway, so I don't believe that giving it this behavior is out of
line.
In any case, I got around the problem by hacking the code, breaking
keywords in the process, but I would like to see a real solution in
the main repository that still provided keyword support.
On the other topic, I haven't been able to discern what status '[' and
']' have been given in Kawa's Scheme system. They seem to do
SOMETHING, but its unclear to me what it is.
[+ 2 3 ] ==> 5
[+ 2 3] ==> ...prompts for further input with
something like #|[---:100|# (I noticed
its a '[' and not a '(', so obviously
something special is going on) and
when I do type some closing brackets,
things break.
Is thips just some special casing of brackets to deal with array types,
and I am exploring dark dark terrain that I shouldn't be poking my
nose into?
-Felix