= Custom Key Bindings =

As of version 0.5, the user may specify custom key bindings in their `.haskeline` file.  The two new settings are:
 - {{{bind: <key> <keys>}}} (bind the first key to the actions of the second key)
 - {{{keyseq: <term> <string> <key>}}} (POSIX-only: add a new key sequence)

where {{{<term>}}} is a terminal name (optional), {{{<string>}}} is Haskell string syntax, {{{<keys>}}} is a space-separated sequence of {{{<key>}}}s, and {{{<key>}}} is either:
 - a single character
 - `f<n>` (a function key)
 - `left, right, down, up`
 - `backspace, delete, home, end, killline`
 - `return, tab, escape`
 - `ctrl-<key>`, `shift-<key>`, `meta-<key>`
 - `pageup, pagedown` (haskeline>=0.6.2)
 
Note that the `meta-` key is `ALT` on Windows.

These features are pretty new, so feedback and suggestions are encouraged.

 == Examples ==

The following lines will cause the backspace key to move one character to the left nondestructively, and meta-backspace to delete the character to the left of the cursor:
{{{
bind: backspace left
bind: meta-backspace backspace
}}}

=== Vi-style History ===

(See ViModeCompatibility.)

=== Control-left/right ===

The following instructions will make `ctrl-left` and `ctrl-right` skip words.

First, we check KeyBindings to see that `M-B` and `M-F` are bound by default to the commands we want.  So the necessary `bind` commands are:
{{{
bind: ctrl-left meta-b
bind: ctrl-right meta-f
}}}

That's sufficient on Windows, but for POSIX systems a couple more steps are needed.  Normally Haskeline looks up a key sequence in the system `terminfo` database; however `ctrl-left` and `ctrl-right` don't have a standard capability name, so Haskeline needs to be told manually what their key sequence is.  

To find out their control sequences, you can do something like:
{{{
$ ghc -e getLine
<press ctrl-left, then return>^[[5D
"\ESC[5D"
$ ghc -e getLine
<press ctrl-right, then return>^[[5C
"\ESC[5C"
}}}

Thus we add the following lines (which will be ignored on Windows):
{{{
keyseq: "\ESC[5D" ctrl-left
keyseq: "\ESC[5C" ctrl-right
}}}

Finally, we may want to restrict the above key sequences to a given terminal (as selected by the $TERM variable).  For example, on my system I have:
{{{
keyseq: xterm-color "\ESC[5D" ctrl-left
keyseq: xterm-color "\ESC[5C" ctrl-right
keyseq: xterm "\ESC[1;5D" ctrl-left
keyseq: xterm "\ESC[1;5C" ctrl-right
}}}
since `$TERM==xterm-color` means I'm using OS X's Terminal.app program, and `$TERM==xterm` means I'm using the X11 `xterm` program.

=== Sequence macros ===
Originally suggested by Trent Buck:
{{{
bind: { { } left
bind: ( ( ) left
bind: [ [ ] left
bind: } right
bind: ] right
bind: ) right
}}}
These bindings automatically closes each opening brace; for example, pressing {{{'('}}} will first insert {{{"()"}}} and then move the cursor one character to the left.