Emacs needs truely useful flex matching

[Le Wang]

Hi all,

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.


--
Le