C++ Primer, Fifth Edition

Function Parameter List

A function’s parameter list can be empty but cannot be omitted. Typically we define a function with no parameters by writing an empty parameter list. For compatibility with C, we also can use the keyword void to indicate that there are no parameters:

void f1(){ /* ... */ }     // implicit void parameter listvoid f2(void){ /* ... */ } // explicit void parameter list

A parameter list typically consists of a comma-separated list of parameters, each of which looks like a declaration with a single declarator. Even when the types of two parameters are the same, the type must be repeated:

int f3(int v1, v2) { /* ... */ }     // errorint f4(int v1, int v2) { /* ... */ } // ok

No two parameters can have the same name. Moreover, ...