[htdig] How to search words like c++

[<jay...@or...>]

Hi,
I have installed htdig and it is working. The part of site is documentation on 
c++. There are hundreds pages with c++ in it.

When I search by giving "c++" in the query (I'm using default search.html came 
with ht://dig), It is showing no matches.

"No matches were found for 'c and '"

How do I enable queries similar to this?

Regards
jayan