Question

This question is nearly identical to this question except that I have to go to three spaces (company coding guidelines) rather than four and the accepted solution will only double the matched pattern. Here was my first attempt:

:%s/^\(\s\s\)\+/\1 /gc 

But this does not work because four spaces get replaced by three. So I think that what I need is some way to get the count of how many times the pattern matched “+” and use that number to create the other side of the substitution but I feel this functionality is probably not available in Vim’s regex (Let me know if you think it might be possible).

I also tried doing the substitution manually by replacing the largest indents first and then the next smaller indent until I got it all converted but this was hard to keep track of the spaces:

:%s/^              \(\S\)/                     \1/gc

I could send it through Perl as it seems like Perl might have the ability to do it with its Extended Patterns. But I could not get it to work with my version of Perl. Here was my attempt with trying to count a’s:

:%!perl -pe 'm<(?{ $cnt = 0 })(a(?{ local $cnt = $cnt + 1; }))*aaaa(?{ $res = $cnt })>x; print $res'

My last resort will be to write a Perl script to do the conversion but I was hoping for a more general solution in Vim so that I could reuse the idea to solve other issues in the future.

Answer 1

Let vim do it for you?

:set sw=3<CR>
gg=G

The first command sets the shiftwidth option, which is how much you indent by. The second line says: go to the top of the file (gg), and reindent (=) until the end of the file (G).

Of course, this depends on vim having a good formatter for the language you’re using. Something might get messed up if not.

Regexp way… Safer, but less understandable:

:%s#^\(\s\s\)\+#\=repeat(' ',strlen(submatch(0))*3/2)#g

(I had to do some experimentation.)

Two points:

• If the replacement starts with \=, it is evaluated as an expression.
• You can use many things instead of /, so / is available for division.