Functions

Functions are C++ entities that associate a sequence of statements (a function body) with a name and a list of zero or more function parameters.

// function name: "isodd"
// parameter list has one parameter, with name "n" and type int
// the return type is bool
bool isodd(int n)
{                 // the body of the function begins
    return n % 2;
}                 // the body of the function ends

When a function is invoked, e.g. in a function-call expression, the parameters are initialized from the arguments (either provided at the place of call or defaulted) and the statements in the function body are executed. If the parameter list ends with ..., extra arguments can be supplied to the function, such a function is called variadic function.

int main()
{
    for (int arg : {-3, -2, -1, 0, 1, 2, 3})
        std::cout << isodd(arg) << ' '; // isodd called 7 times, each
                                        // time n is copy-initialized from arg
}

Unqualified function names in function-call expressions are looked up with an extra set of rules called "argument-dependent lookup" (ADL).

A function can terminate by returning or by throwing an exception.

A function declaration may appear in any scope, but a