bool check_extension ( char* name )
// checks whether an extension is supported
{
	char*	list;

	// get a list of supported extensions
	list = ( char* ) glGetString ( GL_EXTENSIONS );

	if ( !name || !list )
	// if something is wrong
		return false;

	while ( *list )
	// loop through list
	{
		// find the length of the first extension substring
		unsigned int first_extension_length = strcspn ( list, " " );

		if ( strlen ( name ) == first_extension_length && strncmp ( name, list, first_extension_length ) == 0 )
		// if extension is supported
			return true;

		// move to the next substring
		list += first_extension_length + 1;
	}

	return false;
}

void init_extensions ( )
// initializes extensions
{
	if ( !check_extension ( "GL_ARB_multitexture" ) )
		return_error ( fatal_error, "Failed to load GL_ARB_multitexture extension. Your system doesn't support it." );

	if ( !check_extension ( "GL_ARB_vertex_shader" ) )
		return_error ( fatal_error, "Failed to load GL_ARB_vertex_shader extension. Your system doesn't support it." );

	if ( !check_extension ( "GL_ARB_fragment_shader" ) )
		return_error ( fatal_error, "Failed to load GL_ARB_fragment_shader extension. Your system doesn't support it." );
}