Question

According to this site the static methods

static Point rectangular(float x, float y);    
static Point polar(float radius, float angle);

invoke the private constructor Point (a non-static method) as reproduced below :

#include <cmath>               // To get std::sin() and std::cos()

class Point {
 public:
   static Point rectangular(float x, float y);      // Rectangular coord's
   static Point polar(float radius, float angle);   // Polar coordinates
   // These static methods are the so-called "named constructors"
   ...
 private:
   Point(float x, float y);     // Rectangular coordinates
   float x_, y_;
 };

 inline Point::Point(float x, float y)
   : x_(x), y_(y) { }

 inline Point Point::rectangular(float x, float y)
 { return Point(x, y); }

 inline Point Point::polar(float radius, float angle)
 { return Point(radius*std::cos(angle), radius*std::sin(angle)); }
};

Edit: I’m having difficulties accepting an answer, since I don’t know which one is correct.

Answer 1

A constructor is a special case, because a constructor doesn’t need an existing object to be called.

The rule you mention would be better remembered as “A static member function doesn’t have an implicit this pointer”.