How to replace a character with another character by character code

Question

I want to write a command that replaces all of a line's spaces with figure spaces, and I want the code to not use those literal characters so it is more legible than :s/ / /g

So, naturally, I try various iterations like:

:s/\x20/\u2007/g      " matches a hex char then "20", adds uppercase "2007"
:s/\%u20/\%u2007/g
:s/[\x20]/\\%u2007/g
:s/[\x20]/^Vu2007/g                " that's a literal <Ctrl-V>
:s/\%u20/\=printf("%c", 0x2007)/g  " gives me ^G instead
:s/\%u20/\="\<Char-0x2007>"/g      " gives me <e2><80><fe>X<87> instead

None of these work, though all of the patterns do indeed match spaces.

I see lots of tricks around for how to enter Unicode characters in Insert mode, but none about how to do so in a replacement string.

In researching this question, I found How to translate Unicode escape sequences to the Unicode character, which gives me the following functional solution:

:s/\%u20/\=nr2char(0x2007)/g

Is there really no cleaner way to do this? I assume that's unnecessarily costly.

Answer 1

I'm surprised you didn't see an error message telling you that there was no match. Your problem is \x20 which was matching nothing. Your pattern was effectively:

[0-9A-Fa-f]20

\x matches a hex digit atom. See :h /\x. What you're thinking of are string special characters (:h expr-quote), which aren't expanded in patterns.

This is what you want:

execute ":s/ /\u2007/g"

or

:s/ /\="\u2007"/g

or

:s/\%u20/\="\u2007"/g

Just use a literal space as the pattern.