How to convert series of commands into a Vim Function?

Question

I currently run a series of commands on any file I am working on to compress the lines. That series is -

G:a
PRESS ENTER KEY
.
:g/^./ .,/^$/-1 join

So I press S-g, S-:, a, enter, ., then run that regular expression. This joins my lines.

function! CrunchLines()
exec G
exec :
exec  a
exec return
.
:g/^./ .,/^$/-1 join
endfu
com! CRUNCH call CrunchLines()

How do you just run vim commands inside of a function?

Answer 1

If you want to run a command from a vim function you can do so with the normal command :

normal! dd 

This act as dd in normal mode. The ! prevent using user mapping, to you get the basic vim functionalities.

Now to compress your file you can go to the last line with G and then joins every lines with your expression.

So the function could be :

function! Crunch() abort
  normal! G
  g/^./ .,/^$/-1 join
endfunction

You can also use the J key that joins the lines like so :

function! Crunch() abort
  normal! ggVGJ
endfunction

Decomposing :

gg  : go to first line
V   : start a visual line selection
G   : go to last line
J   : join the selection

Answer 2

My exact method was -

" Crunch multi line text into single line
" Useful for moving text from .tex to web services
function! Crunch() abort
    normal! G
    normal! o
    g/^./ .,/^$/-1 join
endfunction
com! CRUNCH call Crunch()

This allows me to crunch multi line files correctly.