Re: Splicing lists and vectors into argument lists

[Per Bothner <per@bothner.com>]

On 05/10/2014 11:49 AM, Helmut Eller wrote:
> On Sat, May 10 2014, Per Bothner wrote:
>
>> A issue is that initial '@' in a symbol is *not* allowed by R7RS or
>> R6RS. ('@' is a <special subsequent> so is not allowed as an initial
>> character.)
>
> Oh boy.  They let you put Unicode chars there but no @.  Oh wait, they
> actually say "it is an error for the first character to have a general
> category of Nd, Mc, or Me."  But @ belongs to category Po.  And again
> they use the meaningless phrase "it is an error" which of course only
> means that it may or may not be allowed by an implementation.

I just noticed the r7rs errata:
http://trac.sacrideo.us/wg/wiki/R7RSSmallErrata

     7, In Section 7.1.1, the lexical rule <special initial> incorrectly omits @.

Since (in my reading) r6rs also allows an initial '@', I think it would be
correct for the --r7rs/--r6rs/--r5rs flags to disable the '@' reader
mapping from @EXPR to ($splice$ EXPR).  (r5rs doesn't allow an initial '@',
but allowing it would still be a compatible extension, so for simplify
--r5rs behaves the same.)

So I checked in a fix for this:

$ kawa --r7rs
#|kawa:1|# (define @ 3)
#|kawa:2|# (define @2 2)
#|kawa:3|# (+ @ @2)
5
-- 
	--Per Bothner
per@bothner.com   http://per.bothner.com/