On Fri, Sep 06, 2002 at 02:20:10PM +0100, Piers Cawley wrote:
> Nicholas Clark <[EMAIL PROTECTED]> writes:
>
> > On Wed, Sep 04, 2002 at 10:46:24PM -0400, Ken Fox wrote:
> >> What is really needed is something that converts the date syntax
> >> to normal Perl code:
> >>
> >> rule iso_date { (<Perl.term>) -
> >> (<Perl.term>) -
> >> (<Perl.term>)
> >> { use grammar Perl::AbstractSyntax;
> >> $0 := (expr (invoke 'new (class 'Date) $1 $2 $3))) }
> >
> > I'm confused. Why has that last line got a lisp expression for the spliced
> > in code?
>
> 'cos S expressions are a relatively simple way of writing a syntax tree?
But it's in the middle of stream of perl.
Except, if I understand things correctly, the way the perl parsing rules
work, it would be quite legal for any perl grammar to say that the next
argument is to be written as an S expression *directly and raw in the source
code*, and the parser will happily then read one S expression to its
terminator, before continuing in perl (well, more conventional perl) syntax.
ie Ken's code, above, could well be completely legal perl6 code.
This idea of just switching language syntax in a context-sensitive way is
trying to make my head explode.
Nicholas Clark
