substitute with modified matched with :s

Question

I want to change :

int i = libfnc1();
float j = libfnc2();
libfnc3();

to

int i = lib::libfnc1();
float j = lib::libfnc2();
lib::libfnc3();

using :s

I want to do somthing like :s/libfnc[0-9]/lib::**MATCHED**/g but I haven't found what to put in place of MATCHED

Answer 1

You can use either & or \0 for this:

:%s/libfnc[0-9]/lib::&/g 

See :help sub-replace-special for more details.

An alternative approach is to exclude the libfnc... part from the match, by ending the match with \ze:

:%s/\zelibfnc[0-9]/lib::/g

This will search for the entire expression libfnc[0-9] but will only include the part before the \ze (in this case, nothing) in the replacement.