Re: Looking for volunteers for XL

On Nov 28, 6:50 am, Timothy Knox <t...@thelbane.com> wrote:
> Somewhere on Shadow Earth, at Mon, Nov 28, 2011 at 04:45:11AM +0000, Kaz
Kylheku wrote:
>
> > [Are you aware of anyone actually doing this? I agree that you might
> > expect extensible languages to be handy design testbeds, but somehow
> > other than in the Lisp community, it didn't work out that way. -John]
>
> Well, John, I think the Forth community provide another counter-example.
> Granted, I am not aware of any projects of hundreds or thousands of
> Forth devs, but some rather significant projects have been done in Forth
> by small teams. And lest folks think Forth as a philosophy is dead, you
> might want to seehttp://factorcode.org/where the language is evolving
> in some very interesting directions.
> --
> Timothy Knox <mailto:t...@thelbane.com>
>
> Never trust a language where its users won't tell you that it sucks.
> -- Peter Corlett, on We Hates Software (about Python)
> [Forth is swell, but you can't extend its syntax the way you can in
> languages with BNF-based parsers and rewrite rules. -John]


To John's observation; perhaps its lack of syntax makes it seem that
way, but Forth programmers are dab hands at extending Forth. Want new
control structures beyond the basics? Not a problem; here's a CASE
ENDCASE constructed from Forth primitives, since the programmer has
access to the compiler; (comments are in ( ) or preceded by \ );


: case ( -- 0 ) 0 ; immediate
: of ( C:
                ( x -- )
                1+ >r
                postpone over postpone =
                postpone if postpone drop
                r> ; immediate
: endof ( C: orig1
                >r postpone else r> ; immediate
: otherwise ; immediate
: endcase ( c: orig1..orign
                postpone drop
                0 ?do postpone then loop ; immediate


Now we can...


: testcase ( n -- )
    case 1 of ." one" endof
              2 of ." two" endof
              otherwise ." a lot"
    endcase ;
[Hey, I said forth is swell. But there isn't a real parser, and if you get
your syntax slightly wrong, rather than parser errors, you get exciting
stack explosions. -John]