Re: [Gnu-arch-users] new language, arch, furth, etc.

[Tom Lord]

    > From: Colin Walters <address@hidden>

    > On Mon, 2004-07-19 at 20:40 -0700, Tom Lord wrote:

    >>  set-in-version: (upstream "address@hidden/tla--devo--1.3")

    > Or you might just say:

    > X-Upstream: address@hidden/tla--devo--1.3

    > No need for a language for this.


Oops... you are mistaken.  You contradict yourself.

Answer me this.... Why is _this_ an example of a language in use:


       set-in-version: (upstream "address@hidden/tla--devo--1.3")

but _this_ is not:

       X-Upstream: address@hidden/tla--devo--1.3

It seems to me that you really wanted to say

   We already have a langauge for this kind of thing.  The language is
   (roughly):

        program := X-<name>: <value>

        <name> := <alnum and some punctuation>+

        <value> := <RFC822 header field contents>

For very simple settings, such as setting "upstream" to a
fully-qualified version name, that traditional language is, indeed,
quite ample.

What if, though, the value is supposed to be a list?   Or nested
lists? or numbers?  or a string that can contain arbitrary characters?
or a list of such strings?

What if the value of the variable isn't a constant but should be
computed in some way?

My issues with the traditional language you describe boil down to its
being too weak: it doesn't answer questions like those I've listed
above.   At the very least we'll want to supplement that traditional
language definition with some additional rules.   One rule might be:

        * a list value is a white-space separated sequence of elements

That would be a lousy rule, of course, since it would mean that
elements may not contain spaces and since it would fail to permit 
nested lists.

So: let's anticipate those kinds of issues -- note what kinds of
values we need and perhaps what kinds of computation -- and design a
set of those rules that actually works.  That's what I've been engaged
in.


-t