Emacs regex replace while re-using part of the expression in the replacement

Question

I sometimes need to do replacements which would involve using matched parts for the output.

For example, I would like to replace

varName->doWork()

with

::doWork(varName, 42)

whatever varName actually is.

Is there a straightforward way to do this?

Answer 1

It's doable. M-x query-replace-regexp:

• from: ^\(\w+\)->\([^(]+\)()
• to: ::\2(\1, 42)

But if it's a recurring pattern, it's best to solidify it in a function, instead of entering the regex each time.