[r6rs-discuss] @ should be a valid identifier

[Derick Eddington]

I believe the spirit of the R6RS is to allow @ to be an identifier.  To
use SXML/SSAX, we *really* need @ to be a valid identifier.

Following my comments below, I cannot see a reason why @ should not have
been allowed to be an identifier.  Is there a good reason @ should not
be a valid identifier?


R6RS 4.2.4:

In general, a sequence of letters, digits, and "extended alphabetic
characters" is an identifier when it begins with a character that cannot
begin a representation of a number object.

Extended alphabetic characters may be used within identifiers as if they
were letters. The following are extended alphabetic characters:

! $ % & * + - . / : < = > ? @ ^ _ ~

4.2.1:

<special initial> -> ! | $ | % | & | * | / | : | < | = | > | ? | ^ | _ | ~
<special subsequent> -> + | - | . | @
<peculiar identifier> -> + | - | ... | -> <subsequent>*


I believe not including @ in <special initial> (which would mean it
doesn't need to be in <special subsequent>), or at least in <peculiar
identifier>, was a mistake because @ "cannot begin a representation of a
number object", opposed to . which can.

As you can see in 4.2.1, the only place @ is used in numbers is:

<complex R> -> <real R> @ <real R>

and a <real R> cannot be <empty>.

-- 
: Derick
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