How can I map `Ctrl+Alt+Char` and `Ctrl+Number` in vim on Mac OSX?
If you use MacVim, the easiest way is:

set macmeta


So that MacVim will treat alt/option as Meta key, you can then bind:

nmap &lt;C-M-S&gt; :call foo_func()


The keys pressed for above is: Ctrl+alt+s.

Hope this helps and solves your issue, happy Vimming!