What exactly is or was the purpose of C++ function-style casts?

Question

I am talking about \"type(value)\"-style casts. The books I have read pass over them quickly, saying only that they are semantically equivalent to C-style casts, \"(type) va

Answer 1

Function style casts bring consistency to primitive and user defined types. This is very useful when defining templates. For example, take this very silly example:

template
T silly_cast(U const &u) {
  return T(u);
}

My silly_cast function will work for primitive types, because it's a function-style cast. It will also work for user defined types, so long as class T has a single argument constructor that takes a U or U const &.

template
T silly_cast(U const &u) {
    return T(u);
}

class Foo {};
class Bar {
public:
    Bar(Foo const&) {};
};

int main() {
    long lg = 1L;
    Foo f;
    int v = silly_cast(lg);
    Bar b = silly_cast(f);
}