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Re: [Txr-users] use regex in filter?

From: 苏灵
Subject: Re: [Txr-users] use regex in filter?
Date: Sat, 13 Jul 2013 01:04:28 +0800

2013/7/12 Kaz Kylheku <address@hidden>
> On Thu, 11 Jul 2013 19:11:07 +0800, 苏灵 <address@hidden> wrote:
> > I am new to TXR. Txr is a powerful tool that make things simple.
> > filter is amazing, but when i want to use regex in filter to do some
> > replacement, i don't know how to implement.
> >  Is it possible to use regex in filter? If it is ,how?
> Not currently. The filter stuff has its own algorithm based on tries.
> This would
> have to be extended to encompass regexes. I have some ideas how to do
> that;
> maybe I can make it a priority for the next release.

At your convenience. TXR is already a powerful language,
I can do the same thing in another way. It is just instinctive to
use "filter" to do some replacements. I think it is necessary to
make the powerful TXR more simple, and more elegant.

> There is already a hybridization going on in the trie data structure in
> that a node of the tree can be a function which takes over the matching
> from that node downward. This allows the :fromhtml filter to work,
> which
> has to be able to recognize sequences of digits for the character
> escape
> which takes the form: &#<digits>;
> Regex filtering can be done using TXR Lisp, via the regsub function,
> but that's not satisfactory if you want to replace multiple regexes
> with multiple replacements.
> A pattern-matching function can be used for filtering also. Look for
> the section "Function Filters" in the manual.  The idea is that you can
> write a two-argument pattern function which analyzes the first argument
> and binds the second one to some output. This can then be used in
> filters
> with the (:fun <function-name>) syntax. But this has to handle the
> complete
> text in one call, performing all necessary replacements on it.

I am just trying this way tonight. But the codes turn out a little messy.

> > BTW, some directives is not easy to understand, more example will
> > help.
> That's right; the goal so far had been just to make the documentation
> complete
> in terms of feature coverage. Examples are lacking in many places.

I am still reading the documentation. Sometimes, it is difficult to
understand the philosophy of  txr. More example is necessary.

I am planing to translate the documentation to Chinese, at least partially.

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