How to invert the selection in vim?

Question

After selecting a range of lines with the V command, I would like to delete every line of the file that is NOT selected.

Edit: What I would really like to know, is if there is a way to invert the selection -- select every line that is not selected. Like how

:g!/FOO/d`

deletes every line which does NOT contain FOO. The inverse of

'a,'b

would be the two ranges:

1,'a-1 and 'b+1,$

I suspect that this cannot be done in one step -- but it would be nice!

Answer 1

First create the following mapping (for example bound to the <F4> key)

map <F4> :<C-U>1,'<-1:delete<CR>:'>+1,$:delete<CR>

then, after selecting a range in visual mode, just press <F4> to trigger the associated command. The command can be easily explained in parts:

• ":" Enter command line mode.
• "<C-U>" Remove all characters between the cursor position and the beginning of the line.
• "1,'<-1" Specifiy the range from the first line of the file to the line before the start of current selection.
• ":delete<CR>" Delete (the previously specified range of lines).
• ":'>+1,$:delete<CR>" Delete the lines in the range "'>+1,$", i.e. from the line after the end of the selection to the end of the file.

Answer 2

1. select your text

2. "*yggdG"*p which means ...

   "*y    " yank it to the selection register
   ggdG   " delete everything
   "*p    " and paste the selection again
   

Answer 3

since 'inverting' means basically to create 'multiselections' (the area before and after the original selection) i searched the vimscripts again http://www.vim.org/scripts/script.php?script_id=953. try this.

 There are a number of operations to very
 easily manipulate selections such as modifying 
 the regions (add/delete/inverte/clear), hiding, 
 refreshing, saving and restoring etc."