Is it possible to exchange search patterns in vim?

Question

Is there a way, built-in or with a plugin, that I can swap any number of two different patterns on an arbitrary range using a regex?

Maybe something :s-style like :{range}exchange/{pattern-1}/{pattern-2}/{flags}?

Example:

foo bar
bar foo bar

hypothetical command swaps foo and bar

bar foo
foo bar foo

Answer 1

This is a duplicate of an old question I cannot found anymore but for which I've a trace (through a solution): https://github.com/LucHermitte/lh-misc/blob/master/plugin/rotate_substitute.vim

:command! -bang -nargs=1 -range CycleSubstitute <line1>,<line2>call s:CycleSubstitute("<bang>", <f-args>)


" no back ref supported; makes no sense
function! s:CycleSubstitute(bang, repl_arg) range
  let do_loop = a:bang != "!"
  let sep = a:repl_arg[0]
  let fields = split(a:repl_arg, sep)
  let cleansed_fields = map(copy(fields), 'substitute(v:val, "\\\\[<>]", "", "g")')
  " build the action to execute
  let action = '\=s:DoCycleSubst('.do_loop.',' . string(cleansed_fields) . ', "^".submatch(0)."$")'
  " prepare the :substitute command
  let args = [join(fields, '\|'), action ]
  let cmd = a:firstline . ',' . a:lastline . 's'
        \. sep . join(fields, '\|')
        \. sep . action
        \. sep . 'g'
  " echom cmd
  " and run it
  exe cmd
endfunction

function! s:DoCycleSubst(do_loop, fields, what)
  let idx = (match(a:fields, a:what) + 1) % len(a:fields)
  return a:fields[idx]
endfunction

Which could be used with: %CycleSubstitute/foo/bar in your example.

Answer 2

Great though it would be, there is no exchange command in Vim and the usual approach here is to perform A-->B, C-->A, B-->C instead of the direct but impossible A<-->C. Of course, one needs to guarantee that the intermediate B value is not present in the file. So use something weird enough for B, for example, @#%:

:%s/foo/@#%/g|%s/bar/foo/g|%s/@#%/bar/g

If you don't want to take the risk of @#% being present in the file, adapt this use of Sed to:

:%!sed 's/foo/\n/g;s/bar/foo/g;s/\n/bar/g'

As described in the linked answer, Sed's pattern space is guaranteed to have no newline characters, so this last command is certain to succeed.

Answer 3

Use capture groups.

:s/\v(pattern1)(.*)(pattern2)/\3\2\1/

You need to capture the text in between to reference it during substitution.