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Re: Character group folding in searches
From: |
Eli Zaretskii |
Subject: |
Re: Character group folding in searches |
Date: |
Sat, 07 Feb 2015 17:31:57 +0200 |
> From: Stefan Monnier <address@hidden>
> Cc: address@hidden, address@hidden
> Date: Sat, 07 Feb 2015 10:02:52 -0500
>
> To me the simplest option is to have a DFA which returns an integer
> (this integer being "the equivalence class number", and which will
> usually be one of the characters in the equivalence class).
>
> Each DFA node could be a char-table. So if all equivalence classes are
> made up of single-chars, the DFA collapses is just a plain-old
> char-table mapping chars to the canonical element of their
> equivalence classes. For 2-char elements, we'll arrange for the
> entry for the first char (in the main char-table) to be not an integer
> but another char-table. Being a DFA, this could easily handle complex
> elements (matching arbitrary regular expressions), tho whether we'd make
> much use of this particular feature is not very important.
I'm sorry, I don't understand how this will solve the use-cases
brought up in this thread. Can you explain?
The use-cases I have in mind are:
. exact match -- only exactly the same codepoints match
. base-character match -- this ignores any combining marks,
diacriticals, etc.
. matching ligatures, such as ffi and ffi
. ignoring punctuation, like string-collate-equalp does,
i.e. "foobar" will match "foo.bar"
. ignoring isolated zero-width or non-combining marks and
directional controls
I understand very well how these can be handled by several different
char-tables, but you seem to say that a single char-table can do all
this, and I don't see how.
Also, what does DFA have to do with all this?
> Since some of the nodes in the DFA would likely only handle a very few
> chars specially, we could later improve the representation so that those
> nodes don't use up a whole char-table.
Now I'm completely confused: char-tables don't need this optimization,
as you well know: they already are space-efficient for storing
characters that map to the table's default value. So I probably
misunderstand your whole idea, if it does need such an optimization.
> PS: And this same kind of "char-table extended into a DFA" could be
> useful for syntax-tables in order to provide much more flexible support
> for multi-character comment markers or "paren-like nested elements".
If that's your itch to scratch, I'm impatiently waiting for patches ;-)
- Re: Character group folding in searches, (continued)
- Re: Character group folding in searches, Eli Zaretskii, 2015/02/06
- Re: Character group folding in searches, Artur Malabarba, 2015/02/06
- Re: Character group folding in searches, Eli Zaretskii, 2015/02/06
- Re: Character group folding in searches, Artur Malabarba, 2015/02/06
- Re: Character group folding in searches, Eli Zaretskii, 2015/02/07
- Re: Character group folding in searches, Stefan Monnier, 2015/02/06
- Re: Character group folding in searches, Eli Zaretskii, 2015/02/06
- Re: Character group folding in searches, Stefan Monnier, 2015/02/06
- Re: Character group folding in searches, Eli Zaretskii, 2015/02/07
- Re: Character group folding in searches, Stefan Monnier, 2015/02/07
- Re: Character group folding in searches,
Eli Zaretskii <=
- Re: Character group folding in searches, Stefan Monnier, 2015/02/08
- Re: Character group folding in searches, Eli Zaretskii, 2015/02/08
- Re: Character group folding in searches, Stefan Monnier, 2015/02/08
- Re: Character group folding in searches, Eli Zaretskii, 2015/02/09
- Re: Character group folding in searches, Stefan Monnier, 2015/02/09
- Re: Character group folding in searches, Eli Zaretskii, 2015/02/09
- Re: Character group folding in searches, Stefan Monnier, 2015/02/09
- Re: Character group folding in searches, Eli Zaretskii, 2015/02/10
Re: Character group folding in searches, Juri Linkov, 2015/02/06