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//====================================================================
// Library code: implementing the metaclass (once)
$class basic_value {
basic_value() = default;
basic_value(const basic_value& that) = default;
basic_value(basic_value&& that) = default;
basic_value& operator=(const basic_value& that) = default;
basic_value& operator=(basic_value&& that) = default;
constexpr {
for... (auto f : $basic_value.variables())
if (!f.has_access()) f.make_private();
for... (auto f : $basic_value.functions()) {
if (!f.has_access()) f.make_public();
compiler.require(!f.is_protected(), "a value type may not have a protected function");
compiler.require(!f.is_virtual(), "a value type may not have a virtual function");
compiler.require(!f.is_destructor() || f.is_public(), "a value destructor must be public");
}
}
};
$class value : basic_value { };
//====================================================================
// User code: using the metaclass to write a type (many times)
value Point {
int x = 0, y = 0;
Point(int xx, int yy) : x{xx}, y{yy} { }
};
Point get_some_point() { return {1,1}; }
int main() {
Point p1(50,100), p2;
p2 = get_some_point();
p2.x = 42;
}
// Compiler Explorer note: Click the "triangle ! icon" to see the output:
constexpr {
compiler.debug($Point);
}
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