On Wed, Apr 17, 2002 at 05:43:01PM -0400, Dan Sugalski wrote:
> At 10:16 PM +0100 4/17/02, Dave Mitchell wrote:
> >On Wed, Apr 17, 2002 at 04:57:21PM -0400, Dan Sugalski wrote:
> >> At 9:48 PM +0100 4/17/02, Dave Mitchell wrote:
> >> >On Wed, Apr 17, 2002 at 04:34:12PM -0400, Simon Glover wrote:
> >> >> I thought lexicals were going to live in a symbol table now? In which
> >> >> case, they're definitely going to depend on implementing hashes first.
> >> >
> >> >The first does not necessarily imply the second.
> >>
> >> True, but in this case it does. Symbol tables are hashes, as are the
> >> lexical scratchpads. (Hashes you can look up by integer index, mind,
> >> but hashes nonetheless)
> >
> >I'm not yet convinced that hashes are the best data structure for
> >lexical symtabs, given their heirarchical and dynamic nature.
> >But lets not get into that debate just now :-)
>
> Oh, hashes are exactly what we want, but they're *special* hashes. :)
>
> The hash PMC types used by symbol tables have the interesting
> property of being able to look entries up by offset, not by key, and
> the offset is determined by insertion order.
>
> The perl 6 equivalent would be:
>
> %foo = ('a', 1, 'b', 2, 'c', 3);
> print %foo[2]
>
> printing 3. Access by offset is fast, so we're fine. (We may even
> peek under the hood, just to be Extra Evil)
>
> At the moment, we don't have to support cascading lexical
> scratchpads--since we know at compile time which variables we're
> accessing and where they come from, we can install trampoline entries
> in the current scope's scratchpad and not have to search outward at
> runtime.
Hmmm, I think I still stand by both the statements I made:
1) I'm not yet convinced that hashes are the best data structure for
lexical symtabs, given their heirarchical and dynamic nature.
2) But lets not get into that debate just now :-)
:-))
--
"Do not dabble in paradox, Edward, it puts you in danger of fortuitous
wit." Lady Croom - Arcadia
