def add_type_converter(type, r2c, c2r)
      warn "WAR\NING: overridding #{type} on #{caller[0]}" if @@type_map.has_key? type
      @@type_map[type] = [r2c, c2r]
    end
def add_type_converter(type, r2c, c2r)
      warn "WAR\NING: overridding #{type} on #{caller[0]}" if @@type_map.has_key? type
      @@type_map[type] = [r2c, c2r]
    end
Registers C type-casts +r2c+ and +c2r+ for +type+.