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

:%!awk -- '++c\%2'

alternatively

:%!awk -- 'c++\%2'

depending on which half you want to weed out.