I've setup a simple vim environment for C++ development and I use clang_complete for code completion. I'm wondering if there is a way to invoke clang_complete with ctrl+space (as in Eclipse for example)? Currently it is invoked with C-X C-U, which is not very convenient. In the plugin code I saw this: inoremap <expr> <buffer> <C-X><C-U> <SID>LaunchCompletion() So I tried something like this in my vimrc: inoremap <expr> <buffer> <C-Space> <SID>LaunchCompletion() Of course it didn't work:) I read vim's doc about key mapping. but no good. Have you got any suggestions what I'm doing wrong?