VIM, auto Completion

IF you are only interested in auto-completing long words as you type, then you look here.   Basically it says :

The function A_Very_Long_Function_Name() can be quite exasperating to type over and over again. While still in insert-mode, one can auto-complete a word by either searching forwards or backwards. In function, Another_Function() one can type A_Very... and hit CTRL-P. The first matching word will be displayed first. In this case it would be A_Very_Long_Variable_Name. To complete it correctly, one can hit CTRL-Pagain and the search continues upwards to the next matching word, which is A_Very_Long_Function_Name. As soon as the correct word is matched you can continue typing. VIM remains in insert-mode during the entire process.




However, if you are interested in having declarations for all functions available in C++ or in a library, you need to use ctags.  A very good explanation of the process to set it up is available here. It is quite long. I would just enumerate the steps for the sake of brevity. I tried it on both Debian 5.0 and Ubuntu 9.10 and it works perfectly. 

1. Install exuberant-ctags
   
   $ sudo apt-get install ctags
   
   
2. Download omnicppcomplete package and extract the zip file into your ~/.vim/ folder. After this .vim folder should look something like this. It may contain other folders depending on the original content of your .vim folder. IF you don't have a .vim folder in your home directory, then create now.
   
   $ cd ~/.vim
   $ ls
   after  autoload  doc  ftplugin omnicppcomplete-0.41.zip
   
   
3. Generate tags for C++ . ctags generates a file called "tags". You should rename it to something like "cpp.tags". You can have different such files for different libraries.
   
   $ ctags -R --c++-kinds=+p --fields=+iaS --extra=+q /usr/include/c++
   $ mv tags cpp.tags
   
4. Now add following lines to ~/.vimrc file
   
   set tags+=~/.vim/cpp.tags
   set nocp
   filetype plugin on
   map  :!ctags -R --c++-kinds=+p --fields=+iaS --extra=+q .
   
   Last command maps CTRL-F6 to generate tags in the current directory directly from vim editor.
   
   
5. Open Vim and run following command to see the help files related omnicomplete.
   
   :helptags $HOME/.vim/doc
   :h omnicppcomplete