I would like to turn a list like this

these are
custom regex expressions 4
syntax? syntax
weird one 3
there are many many many many words in this line 3

into this

these are
custom {4}regex {4}expressions
syntax? syntax
weird {3}one
there {3}are {3}many {3}many {3}many {3}many {3}words {3}in {3}this {3}line

I know how to get rid of the trailing number ending

:%s/ \d\+$//

I know how to replace spaces

:s/ / {3}/g

but how do I combine these two? The second should only apply to lines that actually ended in a number, and use that number.

In my head this problem formed a "substitution in a substitution" thing, like this:

:%s/\(.\+\) \(\d\+\)$/\1.replace(' ', ' {\2}')/

But there is likely a better, VIM, way to solve this. Maybe my conceptualised solution is not supported.

Please how can I perform such operations?

  • 1
    Would something like this work? :g/\d$/s/ /\=' {' . matchstr(getline('.'), '\d\+$') . '}'/g This use a :g command to match only lines ending with w number and applies a substitution command using an expression composed of ' { i.e the space and the first bracket concatenated with matchstr(getline('.'), '\d\+$') which gets the number at the end of the line. You'll probably need to clean up the remaining trailing digits with :%s/\d\+$//
    – statox
    May 12, 2020 at 9:40
  • 1
    Your instinct was kinda on the right track. In general, if you have a substitution problem that can be expressed along the lines of "match a pattern then within the matched string match another pattern [and substitute]" you're often going to need sub-replace expressions . That's what statox's suggestion is using.
    – B Layer
    May 12, 2020 at 12:52
  • 2
    @BLayer would you like to post an answer? Thanks to your link i've figured out the answer ought to be :%s/\(.\+\) \(\d\+\)$/\=substitute(submatch(1), ' ', ' {' . submatch(2) . '}', 'g')/
    – minseong
    May 12, 2020 at 13:32
  • Cool. Glad it was that easy. Go ahead and post an answer yourself, if you'd like. Maybe an upvote for the answer that helped, though...? :) If you'd prefer someone else answer then I'll do it.
    – B Layer
    May 12, 2020 at 13:53
  • @theonlygusti Please turn that into an answer! That's exactly correct, that's what I came here to post, but saw you got to it already. Cheers!
    – filbranden
    May 12, 2020 at 15:00

1 Answer 1


Thanks to B Layer's guidance in the comments and his answer here I've learnt about sub-replace expressions (:help sub-replace-expression)

The command that does exactly what I need is:

:%s/\(.\+\) \(\d\+\)$/\=substitute(submatch(1), ' ', ' {' . submatch(2) . '}', 'g')/

In the replacement part we use the special operator \= which tells Vim to treat everything that follows as an expression, evaluate it, and use the result as the replacement of the matched text

Thanks https://vi.stackexchange.com/a/20706/9024

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