Hi,
In the situation you presented, the & in your "int count1 = count_if(v1.begin(), v1.end(), &lessThan20Function);" line is superfluous. Although it is perfectly good code, and acceptable to all compilers.
In my experience, it would be omitted. By convention.
Also in my experience, there is a preference to function objects over function pointers.
For some really neat stuff, the BOOST (www.boost.org) library has a lambda library, which would allow you to put the body of the predicate right in your count_if statement -- and in a quite abbreviated form. It'd look something like...
int count = count_if(v1.begin(), v1.end(), _1 > 20);
HTH, --Eljay
