"Nicholas Van Weerdenburg" <vanweerd@gmail.com> schrieb im Newsbeitrag news:632154f705010520196f99e845@mail.gmail.com...
"Nicholas Van Weerdenburg" <vanweerd@gmail.com> schrieb im Newsbeitrag
news:632154f705010510264aea7a10@mail.gmail.com...
> Hi all,
>
> I've written a small ruby application that uses YAML and the
> associated hash/array Ruby structure.
>
> I am now looking to do some query-like actions on the basic ruby data
> structure. I'm wondering if there are any packages of
> query-abstractions that make sense for Ruby in a generalized sort-of
> way. E.g. XPath and XQuery for XML, SQL for RDMS, etc.
>
> Currently I've written my structure-parsing code with a few of my
> cases, and I'm starting to refactor with blocks and lambdas in order
> to keep duplication low and offer an easily configurable higher-level
> of abstraction. Now the code is starting to pressure me to create a
> simple query language. Maybe I should go to a ruby db or sqlite, but I
> expect I ultimately only need the most basic functionality.
>
> Any suggestions or recommendations?
Another thought: maybe you can even use Ruby itself. I mean, one can
produce quite readable select expressions in Ruby and we have
Enumerable#all?, #any? etc. You might want to add some functionality for
recursive traversal though.
Kind regards
robert
I like the idea of using Ruby, and have been extending my code in that
manner. However, XML becomes interesting soon because of it's DOM
traversal capabilities.
I'm also wondering if I'm missing some common Ruby/Perl/Python idiom
for handling in-memory data-structure traversal in a more abstract
way, but so far it doesn't look like it.
Does it make sense to have a general data-structure traversal/query
api in a language like Ruby?
I'd say yes, but maybe only for certain types (DOM tree nodes) - not necessarily for general Hash, Array and the like. OTOH you can cook up something quite easily though:
class Object
def traverse() yield self end
end
module Enumerable
def traverse(&b)
each {|o| o.traverse(&b)}
end
end
class Hash
def traverse(&b)
each {|k,v| v.traverse(&b)}
end
end
Note that this does not take care of looks in the object graph. To do that, you need to do a bit more:
class Object
def traverse(context = {}) context[self.id] ||= (yield self; true) end
end
module Enumerable
def traverse(context = {}, &b)
unless context[self.id]
context[self.id] = true
each {|o| o.traverse(context, &b)}
end
end
end
class Hash
def traverse(context = {}, &b)
unless context[self.id]
context[self.id] = true
each {|k,v| v.traverse(context, &b)}
end
end
end
Kind regards
robert
···
On Thu, 6 Jan 2005 05:56:31 +0900, Robert Klemme <bob.news@gmx.net> wrote:
