anchor.diff:          nmap <C-j> :tabp<cr>
           nmap <C-k> :tabn<cr>
   
  -        " deoplete
  -        let g:deoplete#enable_at_startup = 1
  +        " deoplete: enable when entering insert mode to speed up startup
  +        let g:deoplete#enable_at_startup = 0
  +        autocmd InsertEnter * call deoplete#enable()
   
           " <TAB>: completion.
           inoremap <expr><TAB>  pumvisible() ? "\<C-n>" : "\<TAB>"
   
           " automatic rustfmt on save.
   	let g:rustfmt_autosave = 1
  +
  +        " Maintain undo history between sessions
  +        set undofile
  +        set undodir=$HOME/.vim/undodir
         '';
         plug.plugins = with pkgs.vimPlugins // my-nvim-plugins; [
           vim-nix
  
positive.code:         yats-vim # typescript syntax
          deoplete-nvim # async completion
          denite-nvim # async interfaces
          fzf-vim
          fzfWrapper
          rust-vim
          nvim-typescript
          vim-airline
        ];
      };
    };
  
negative.code:           zgen save
          fi
        fi
  
        # vim undo dir
        mkdir -p $HOME/.vim/undodir
      '';
    };
    programs.nix-index.enable = true;
  