Re: Towards (better) Python filters for Pandoc with fluent queries

[Elliott Slaughter <elliottslaughter-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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On Fri, Jan 2, 2015 at 2:34 AM, Mark Szepieniec <mszepien-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> Just from a first glance, wouldn't it be handy to be able to do
>
> m = Matcher()
>     ...
>
> and then
>
> if m.matches(block):
>     ...
>
> This way you could reuse Matchers easily?
>

Thanks; that's the sort of feedback I'm looking for. And yes, I think this
makes sense. To take this a step further, I could imagine supporting
different matching functions for different use cases:

m.match(block) # matches only if the match starts at the root element
m.search(block) # matches if any element at or below the root matches
m.replace(block, replacement_func, count) # replaces up to count
occurrences of the pattern with the result of calling replacement_func

Would that be useful? My immediate need is for the first only, but I could
see cases where I would want the other two.


More generally, I think it makes sense to start thinking of this as more of
a full query language rather than just a way to do pattern matching. Are
there any major features missing that people would want from such a tool?

For example, one might imagine a feature allowing arbitrary subelements to
match. (This is essentially the // operator from XPath.) One potential API
for doing this might look like:

Matcher().Div().contains(Matcher().Emph()) # matches Emphs nested
arbitrarily deep inside a Div

This use case is notable because it is not automatically
backwards-compatible with my current API (it requires the same sort of API
rearrangement as Mark's suggestion above). Are there any other cases like
this? I don't necessarily care if the API is not feature complete on day 1,
but I would still prefer to design things to be forwards-compatible, if
possible. So if you have features you'd like to see, please let me know.


Comments appreciated.


-- 
Elliott Slaughter

"Don't worry about what anybody else is going to do. The best way to
predict the future is to invent it." - Alan Kay

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