Re: [TCLCORE] Argument expansion poll

[Donal K. F. <don...@ma...>]

[Bah!  Why do these things always kick off as soon as I take some time off?]
[And why do I keep sending messages to the wrong destination?  <:^)]

Peter Spjuth wrote:
> Non TCT members are welcome to answer, but please mention that you are
> not TCT.  I value all input but right now my focus is to know what
> the guys with voting power thinks.

So I guess you're definitely interested in my opinion?  ;^)

> 1. Should we aim for a global syntax for argument expansion in Tcl 9?

Yes.

> 2. Should we aim for an expand command for argument expansion in Tcl 8.5?

I'm not at all sure that there should be an 8.5  :^)

Like others have mentioned, I'd rather that any such syntax was available in the
8.* series solely as part as some sort of forward-compatability/migration
package.  Oh, and a warning: I will vote against any alteration to Tcl global
syntax in 8.*, as I think that such a thing should only ever be introduced with
an alteration in major version.

I wonder whether it'd be worthwhile starting a "research" branch in CVS for the
exploration of some of the issues that expansion raises...?

> 3. If yes on any of the above, should it be based on the backtick (`)?
>    Some other syntax?

Backtick and leading brace-pair are the current front-runners.  Backtick has the
disadvantages that can get lost in many fonts and that it doesn't permit fancy
arguments (though I feel that second point is an advantage).  Brace-pair has the
disadvantage that it turns a fairly easily made syntax error into legal syntax.

> 4. How should the syntax work?
> c. Any word starting with ` is expanded if possible. All current word
>    rules apply after the `. Additionally valid constructs:
>    cmd `"[foo $apa] $bepa" `{some words}

Definitely option (c), allowing for whatever the introductory syntax actually
is.  This is because it allows the programmer freedom to write their lists how
they want and allows us to leverage the list parsing rules (which is Good.)

Donal.
-- 
Donal K. Fellows   http://www.cs.man.ac.uk/~fellowsd/   don...@ma...
-- Anyone using MFC desperatly needs a nasal enigma.
                                 -- David Steuber <tra...@da...>