On Wed, Apr 20, 2005 at 10:21:32AM -0700, Larry Wall wrote:
> On Thu, Apr 21, 2005 at 12:50:56AM +0800, Autrijus Tang wrote:
> : I see.  Do you think preserving the /span/ (i.e. the character offset 
> ranges)
> : of each AST element is enough to do that?  That effectively means each
> : node points to a substring inside the original source string.
> Yes, though making a copy isn't bad if it's not the default behavior.
> It mostly just needs a "spot".

Okay.  I'll make it happen then.  Is this something we want to make
available at the runtime language level, in addition to the compiler
error/warnings level?

> p5-to-p5 actually intercepts the op_free() calls and has a place
> for all the optimized trees.  But that's not the default behavior.
> By default it only costs one empty "madprops" pointer per op node.
> (MAD stands for miscellaneous attribute decorations.)  Only if we
> set the "madskills" option do we generate a linked list of madprops.

Wow, nice trick.  Mad props to you. :)

> Then you don't have to worry about the overhead in the general case,
> and you also don't have to worry about your two parses getting out
> of sync in the specific case.  You just have to know in advance when
> you want to remember the details, which I think is not too much of
> a constraint.

As you noted in the followup mail, I think the compiler needs to
remember the active subrule and source code range anyway, so that
performance penalty is already there.

> If you don't want to worry about this in the Haskell version of the
> compiler, that's okay, as long as we think about it more when we
> bootstrap the Perl 6 version.

I do intend to bootstrap the Perl 6 version by simply compiling
the Pugs source code from Haskell into Perl6 AST, then decompile
it back into Perl 6 code. :-)

That is, unless someone crazy enough comes around and recoded
everything in Perl 6 by hand...


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