regex - Emacs - regular expressions in Lisp need to be double-escaped - why?

Question

I've been playing around with emacs lisp, and I wanted to write a little function to do a regular expression search and replace. I had a heck of a time getting the regular expression to work correctly because I didn't realize that all the special characters need to be double escaped when writing lisp code (but not when using query-replace-regexp interactively!).

So for example, using query-replace-regexp interactively you can use

^(.*)[]-.*$

but when writing elisp code you need to double escape everything like so:

^\(.*\)[]-.*$  

I finally found a reference to this in a Steve Yegge article, but I was wondering if anyone knew why this is?

Answer 1

It's because you need to escape backslashes in strings. If you don't escape the backslash of ( in the string, it turns out to be just (