How to delete every other line in Vim?

Question

I would like to delete every other line from a Vim buffer, starting with the second one, i.e., lines 2, 4, 6, etc. For example, if the buffer’s contents is:

a         


        

Answer 1

:map ^o ddj^o
^o

Here ^ stand for CTRL. Recursive macro to delete a line every two line. Choose well your first line and it's done.