Hi there, let's assume I have a structure which takes 5 ints as template parameters. template< int NumChannel , int FirstChannelBits = 0 , int SecondChannelBits = 0 , int ThirdChannelBits = 0 , int FourthChannelBits = 0 , int FifthChannelBits = 0 > struct pixel_type_generator { /* omitted*/ } The first parameter is different as it defines how many of the other parameters are actually used. How can I use boost::preprocessor to get this kind of code repetition: // one channel test pixel_pixel_test< pixel_type_generator< 1, 1 >::type >(); pixel_pixel_test< pixel_type_generator< 1, 2 >::type >(); pixel_pixel_test< pixel_type_generator< 1, 3 >::type >(); pixel_pixel_test< pixel_type_generator< 1, 4 >::type >(); pixel_pixel_test< pixel_type_generator< 1, 5 >::type >(); pixel_pixel_test< pixel_type_generator< 1, 6 >::type >(); // up to 64 // two channels test pixel_pixel_test< pixel_type_generator< 2, 1, 1 >::type >(); pixel_pixel_test< pixel_type_generator< 2, 1, 2 >::type >(); pixel_pixel_test< pixel_type_generator< 2, 1, 3 >::type >(); // ... pixel_pixel_test< pixel_type_generator< 2, 1, 32 >::type >(); pixel_pixel_test< pixel_type_generator< 2, 2, 1 >::type >(); pixel_pixel_test< pixel_type_generator< 2, 2, 2 >::type >(); pixel_pixel_test< pixel_type_generator< 2, 2, 3 >::type >(); // ... // ... pixel_pixel_test< pixel_type_generator< 2, 32, 32 >::type >(); // last two parameters up to 32 - which means there are 32 x 32 calls // three channels test pixel_pixel_test< pixel_type_generator< 3, 1, 1, 1 >::type >(); pixel_pixel_test< pixel_type_generator< 3, 1, 1, 2 >::type >(); // ... // last three parameters up to 21 - which means there are 21 x 21 x 21 calls // four channels test pixel_pixel_test< pixel_type_generator< 4, 1, 1, 1, 1 >::type >(); pixel_pixel_test< pixel_type_generator< 4, 1, 1, 1, 2 >::type >(); // ... // last four parameters up to 16 - which means there are 16 x 16 x 16 x 16 calls // five channels test pixel_pixel_test< pixel_type_generator< 5, 1, 1, 1, 1, 1 >::type >(); pixel_pixel_test< pixel_type_generator< 5, 1, 1, 1, 1, 2 >::type >(); // ... // last four parameters up to 12 - which means there are 12 x 12 x 12 x 12 x 12 calls As you might realize, I try to test every combination until the sum of all channels hits 64. Thanks, Christian