Hi, sorry for another problem... i have a simple question to ask... lets say say i have base class struct GeomObject { // draws an wire shape virtual void drawAbstract(const GLfloat& x, const GLfloat& y, const GLfloat& z) = 0; // draws a solid shape. virtual void drawSolid(const GLfloat& x, const GLfloat& y, const GLfloat& z) = 0; } Now i have bunch of stuff that inherits it.. Like class Circle, class Sphere, class Cylinder, class Cone and all of them implement drawSolid and drawAbstract (radius base assumed). I have a function call drawCircle(const std::string& r, (someBoostFunctionParam)) { Circle cir(4.0, r); // construct a circle with radius 4.0 and name r cir.someBoostFunctionParam(x, y, z); } thus if i say drawCircle("solid", &Circle::drawSolid); drawCircle("abstract", &Circle::drawAbstract); How do you do that? Or whats the best way to do it. On 8/22/06, François Duranleau wrote:

On Mon, 21 Aug 2006, chun ping wang wrote:

[...]

...

template <class T> boost::function getVerxFunc3() { BOOST_STATIC_ASSERT(boost::is_integral<T>::value || boost::is_floating_point<T>::value); return (boost::is_integral<T>::value) ? &glVertex3i : &glVertex3d; }

[...]

...

template <class T> void drawDot(const T& x, const T& y, const T& z) { boost::function myFunc(getVerxFunc3<T>()); glBegin(GL_POINTS); myFunc(x, y, z); glEnd(); glFlush(); }

[just kept one example from the above]

Isn't using boost::function overkill here? I would rather do this:

template < typename T > void gl_vertex( const T& x , const T& y , const T& z ) { // you can use the BOOST_STATIC_ASSERT as above here, or use // boost::enable_if with the same condition around the void return

if ( boost::is_floating_point< T >::value ) { glVertex3d( x , y , z ) ; } else { glVertex3i( x , y , z ) ; } }

or even simply this:

void gl_vertex( GLdouble x , GLdouble y , GLdouble z ) { glVertex3d( x , y , z ) ; }

void gl_vertex( GLint x , GLint y , GLint z ) { glVertex3i( x , y , z ) ; }

and then:

template < typename T > void drawDot( const T& x , const T& y , const T& z ) { glBegin( GL_POINTS ) ; gl_vertex( x , y , z ) ; glEnd() ; }

That should be more efficient and, especially for the second case, is a simpler to read overall.

Anyway, just my two cents.

-- François Duranleau LIGUM, Université de Montréal

"Sacrifices are a necessary factor in creating a new destiny. A small misfortune becomes the cornerstone of a greater happiness." - Emperor Dornkirk, in _The Vision of Escaflowne_

_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

_______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users