Question:

Trying to build pluralize function with vim script

I have this regular expression copied from php script to make plural words

/(?:([^f])fe|([lr])f)$/i \1\2ves

However this does not work with vim

if "calf" =~ "\\v(?:([^f])fe|([lr])f)$" echo "matched" end if

it errors out E64: ? follows nothing

I think I don't fully understand this regular expression, and how can I make it use with vim script?

Vim's regular expression dialect is slightly different from the more common POSIX regexps and Perl-compatible regexps.

The ?: which is used for grouping without capturing the submatch is expressed in Vim as \%(...\) (or \v%(...) in <em>very magic</em> mode). Therefore, you have to use:

if 'calf' =~ '\v%([^f])fe|([lr])f)$'

(Note how I've switched to single quotes to avoid escaping the backslash.)