Re: Emacs needs truely useful flex matching

["Óscar Fuentes" <ofv@wanadoo.es>]

Le Wang <l26wang@gmail.com> writes:

> Since there is a big thread about a standard way to recognise project roots, I
> want to bring up another area in which Emacs is falling behind other
> Editors (Sublime Text, Textmate, and Vim).
> Choosing from a very large list of files (or any strings for that matter) with
> a minimum of keystrokes.
>
> ido-mode has `ido-enable-flex-matching', but that does not do the smart
> sorting required.
>
> Vim has this through the Command-T plugin.  The best way to "get it" is by
> watching it in action:
> https://s3.amazonaws.com/s3.wincent.com/command-t/screencasts/command-t-demo.mov
>
> Skip to 6 minutes to see it in action in a large project with
> repetitive path segments.
>
> Homepage here: https://wincent.com/products/command-t
>
> The matching engine is implemented in C and it interfaces with Vim through the
> Ruby bridge.  I think in order to sort a large list of strings (> 10k), this
> will also have to be implemented in C to be fast enough if done for Emacs.
>
> The sorting algorithm is roughly this for a query: "abcd"
>
> 1. Get all matches for "a.*b.*c.*c"
> 2. Calculate score of each match
>     - contiguous matched chars gets a boost
>     - matches at word and camelCase boundaries (abbreviation) get a boost
>     - matches with smallest starting index gets a boost
> 2. Sort list according to score.
>
> A lot of my colleagues use this kind of flex matching to navigate around our
> large code base in Sublime Text and I'm very jealous that with so few
> keystrokes the most useful
> matches just float to the top.
>
> This navigation could be implemented with Helm if Emacs had a builtin
> fast smart flex sorting engine.

IIUC the vim plugin you mention depends on a pre-built list of files. In
that regard, how is it better than GNU Global, which allows to search
files with a regex (and much more)? Maybe the algorithm you describe
can be implemented on GNU Global and then use an Emacs interface.

I agree that it would be nice to have such a feature native on Emacs,
though. IIRC someone mentioned a few days ago that a regex of the type
you descibe has very high execution complexity (-> is slow) but
obviously it is working for that vim extension.