On Tue, 21 Oct 2008, David Green wrote:
On 2008-Oct-2, at 6:15 pm, Timothy S. Nelson wrote:
The guys on IRC convinced me that the way to go might be something like a
grammar, but that does trees and tree transformations instead of a text
input stream. See the IRC log for details :).
[...]
<TimToady> note to treematching folks: it is envisaged that signatures in a
rule will match nodes in a tree
There does seem to be a clever idea waiting to happen here, although I expect
signatures will be somewhat simpler since they are intended for a more
specific purpose.
One thing I would like signatures to be able to do, though, is assign
parameters by type. Much like a rule can look for identifiable objects like
a <block> or <ident>, it would be very useful to look for parameters by their
type or class rather than by name (or position).
For example, if I ask you to hand me a hammer and a nail, I don't need you to
hand them to me in a specific order, or with labels attached like a Dick
Tracy comic, in order to know which is which. That's obvious, because, well,
one is a hammer and one is a nail. If I'm writing OO-code, then Perl also
knows what's a Tool::Hammer and what's a Fastener::Nail -- if I know that my
$tool is a hammer, and Perl knows, then I shouldn't have to spell it out.
XPath does this by default, and XPath is what I'd want to model any
tree-based stuff on, because it has a pretty comprehensive tree model. But
having said that, I'm not sure that I want to do it by default. It'd
certainly be an option, though.
The :$foo shortcut for :foo($foo) addresses the same problem, but in terms of
naming; it is reasonable that a Foo object would be named "$foo" in both the
caller and the sub, but not necessary. Being able to use class info that's
already there would make it easy to grab params when I know the type of
object I'm looking for, but not what it's called.
I admit to not understanding enough Perl6 to be able to understand
what you're getting at here, but no doubt I will.
:)
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| Name: Tim Nelson | Because the Creator is, |
| E-mail: [EMAIL PROTECTED] | I am |
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