Pointers to Functions

Pointers to functions

A pointer to function can be initialized with an address of a non-member function or a static member function. Because of the function-to-pointer implicit conversion, the address-of operator is optional:

void f(int);
void (*p1)(int) = &f;
void (*p2)(int) = f; // same as &f

Unlike functions or references to functions, pointers to functions are objects and thus can be stored in arrays, copied, assigned, etc.

See also declarations for more information about reading function, pointer, and pointer-to-function declarations.
A pointer to function can be used as the left-hand operand of the function call operator, this invokes the pointed-to function:

Reference:https://en.cppreference.com/w/cpp/language/pointer

int f(int n)
{
    std::cout << n << '\n';
    return n * n;
}
 
int main()
{
    int (*p)(int) = f;
    int x = p(7);
}

Dereferencing a function pointer yields the lvalue identifying the pointed-to function:

int f();
int (*p)() = f;  // pointer p is pointing to f
int (&r)() = *p; // the lvalue that identifies f is bound to a reference
r();             // function f invoked through lvalue reference
(*p)();          // function f invoked through the function lvalue
p();             // function f invoked directly through the pointer

A pointer to function may be initialized from an overload set which may include functions, function template specializations, and function templates, if only one overload matches the type of the pointer (see address of an overloaded function for more detail):

template T f(T n) { return n; }
double f(double n) { return n; }

int main()
{
    int (*p)(int) = f; // instantiates and selects f<int>
}

Equality comparison operators are defined for pointers to functions (they compare equal if pointing to the same function).