Question

Code:

point3f.h

Class Point3f {
     ...
     inline void project2D(ProjType p, const Point2i& view) const;
};

point3f.cpp

inline void Point3f::project2D(ProjType p, const Point2i& view) const {
    switch(p) {
        case PROJ_XY:
            glVertex2f(x * view.x, y * view.y);
            break;
        case PROJ_YZ:
            glVertex2f(y * view.x, z * view.y);
            break;
        case PROJ_XZ:
            glVertex2f(x * view.x, z * view.y);
            break;
        default:
            break;
    }
}

Calling this function raises an error in compile time:

    undefined reference to `Point3f::project2D(ProjType, Point2i const&) const'

I tried every case without and with inline symbol:

inline in header, not in cpp:

 Warning: inline function ‘void Point3f::project2D(ProjType, const Point2i&) const’ used but never defined [enabled by default
 undefined reference to `Point3f::project2D(ProjType, Point2i const&) const'|

inline in header, also in cpp:

 Warning: inline function ‘void Point3f::project2D(ProjType, const Point2i&) const’ used but never defined [enabled by default
 undefined reference to `Point3f::project2D(ProjType, Point2i const&) const'|

inline not in header, but in cpp:

 undefined reference to `Point3f::project2D(ProjType, Point2i const&) const'|

inline not in header, neither in cpp:

 It works but that's not what I want

Question:

1. Does const and inline member function make sense?
2. How to declare a const and inline member function?

Thanks in advance.

Answer 1

The function being const has nothing to do with it. If you want it inline, you must define it in the header file instead of in point3f.cpp. Example:

class Point3f {
    ...
    inline void project2D(ProjType p, const Point2i& view) const
    {
        switch(p) {
        case PROJ_XY:
            glVertex2f(x * view.x, y * view.y);
            break;
        case PROJ_YZ:
            glVertex2f(y * view.x, z * view.y);
            break;
        case PROJ_XZ:
            glVertex2f(x * view.x, z * view.y);
            break;
        default:
            break;
        }
    }
};

In this case, the inline keyword is not needed at all. If you define the function inside the class definition, inline is the default. But you can still specify it, if you want (as I’ve done in the above example.)