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In Haskell-mode, the shortcut C-c C-= is defined to do something.

Trying this shortcut, I realized that emacs do not recognize the shortcut C-c C-=.

Indeed, when I try the shortcut on emacs, the buffer write C-c = is not defined although I pressed C- C-=. I have the same problem with some other symbols like '.' or '§'. But shortcuts like C-c C-l or C-c C-c work.

I try to remove my .emacs but I have the same problem.

a friend have the same problem as me.

Both we are on ArchLinux (64 bits) and we use emacs in console. The keyboard is an azerty.

The problem come from emacs ? Arch Linux ?

Saroupille
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    `C-=` isn't a sequence which most terminals can send. As Emacs is telling you, it's only receiving `=`, not `C-=`. The `C-c` prefix isn't relevant. There are lots of duplicate questions about key binding restrictions in terminals. e.g.: http://stackoverflow.com/a/11118511/324105 – phils Jul 24 '14 at 23:43
  • I did some research but I didn't manage to find the good keywords. Thanks ! – Saroupille Jul 25 '14 at 10:30
  • I'm still unable to find an answer to bind Ctrl+= or Ctrl+. or even Ctrl+| . Where to find the code corresponding to these keybindings ? – Saroupille Jul 25 '14 at 17:25
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    You *can't* bind these key sequences in a terminal Emacs. Terminals have limited key support. Use a graphical Emacs if you want to bind arbitrary keys. –  Jul 25 '14 at 17:30

2 Answers2

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Your terminal can't send Emacs C-= so you can't use that key sequence. (Emacs would recognise it if it received it, but that won't happen.)

Your options are:

  • Run GUI Emacs.
  • Use M-x name-of-command RET (for whatever command is bound to the key sequence you're not able to use). Use C-hm to see the major mode's bindings, or C-hb to see all current bindings, in order to learn what those command names are.
  • Create new custom keybindings for the commands in question (i.e. bindings which your terminal can send to Emacs).
  • Find a different terminal emulator with enhanced key sequence abilities. The vast majority of them will be no better than what you have, because they're all adhering to the limitations of the terminals they're emulating. The most capable one I know of is http://invisible-island.net/xterm/xterm.html but you may need to compile it yourself, and then expect to spend lots of time configuring it. (It's not a trivial solution, though, and xterm requires a GUI environment, so running GUI Emacs is much simpler.)
  • Use C-x@c<key> instead of C-<key>.

With that last option, you can use a sequence your terminal can send to fake a sequence that it can't send.
C-cC-= would become C-cC-x@c=

If you really wanted to use that last option, you can set a custom binding to simplify the sequence (may be necessary in some instances to avoid conflicting with existing sequences). See the end of https://stackoverflow.com/a/24804434/324105 for more information.

Community
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phils
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To add to phils' post - another option is an Emacs package (which I wrote), which can teach Emacs and terminals how to properly recognize all PC keyboard keys and modifier key combinations:

https://github.com/CyberShadow/term-keys

The default configuration already includes encoding key combinations like Ctrl=, as well as similar variations.

Vladimir Panteleev
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