Nicholas Clark <[EMAIL PROTECTED]> writes:
> 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.
But you mean that in a good way right? Anyway, he did introduce the
'use grammar Perl::AbstractSyntax;' in the lexical scope, so obviously
there's *something* afoot...
--
Piers
"It is a truth universally acknowledged that a language in
possession of a rich syntax must be in need of a rewrite."
-- Jane Austen?
