/* * Basically, we are trying to do this in C PreProcessor (a.k.a CPP):: * * int start = 1; * int end = 20; * for (i = start; i != end; i ++) { * for (j = start; j != end; j ++) * printf("%2d x %2d = %3d\n", i, j, (i * j)); * printf("\n"); * } * * References: * goo.gl/1HGxJX * goo.gl/wcfeFK */ #define START (1, ) #define END (0, 2) // this is 20 #define PRINT_FORMAT "%2d x %2d = %3d\n" /* Let's start with some utility functions */ #define EAT(...) #ifndef DEBUG #define TEST(...) EAT #endif #define LITERAL(x) #x #define CAT_0(x, y) x ## y #define CAT_1(x, y) CAT_0(x, y) #define CAT(x, y) CAT_1(x, y) #define EXPAND(...) __VA_ARGS__ #define EMPTY() // empty #define DEFER_0(...) __VA_ARGS__ EMPTY() // defer once #define DEFER_1(...) __VA_ARGS__ DEFER_0(EMPTY) () #define DEFER_2(...) __VA_ARGS__ DEFER_1(EMPTY) () #define DEFER_3(...) __VA_ARGS__ DEFER_2(EMPTY) () #define DEFER_4(...) __VA_ARGS__ DEFER_3(EMPTY) () #define DEFER_5(...) __VA_ARGS__ DEFER_4(EMPTY) () #define DEFER_6(...) __VA_ARGS__ DEFER_5(EMPTY) () #define DEFER_7(...) __VA_ARGS__ DEFER_6(EMPTY) () #define DEFER_8(...) __VA_ARGS__ DEFER_7(EMPTY) () #define DEFER_9(...) __VA_ARGS__ DEFER_8(EMPTY) () #define EVAL_1(...) __VA_ARGS__ /* evaluate 1 time */ #define EVAL_2(...) EVAL_1(EVAL_1(EVAL_1(__VA_ARGS__))) #define EVAL_3(...) EVAL_2(EVAL_2(EVAL_2(__VA_ARGS__))) #define EVAL_4(...) EVAL_3(EVAL_3(EVAL_3(__VA_ARGS__))) #define EVAL_5(...) EVAL_4(EVAL_4(EVAL_4(__VA_ARGS__))) #define EVAL_6(...) EVAL_5(EVAL_5(EVAL_5(__VA_ARGS__))) #define EVAL_7(...) EVAL_6(EVAL_6(EVAL_6(__VA_ARGS__))) #define EVAL_8(...) EVAL_7(EVAL_7(EVAL_7(__VA_ARGS__))) #define EVAL_9(...) EVAL_8(EVAL_8(EVAL_8(__VA_ARGS__))) #define EVAL__1(...) __VA_ARGS__ #define INNER_EVAL(...) EVAL__1(EVAL__1(__VA_ARGS__)) #define IF_1(TRUE_BLOCK, ...) TRUE_BLOCK #define IF_0(TRUE_BLOCK, ...) __VA_ARGS__ #define IIF(cond) CAT(IF_, cond) #define CHECK_N(_, n, ...) n #define CHECK(...) CHECK_N(__VA_ARGS__, 0, 0) #define PROBE(x) x, 1, /* * NOT(0) = 1, NOT(otherwise) = 0 */ #define NOT(x) CHECK(CAT(NOT_, x)) #define NOT_0 PROBE(~) /* * BOOLEAN OPERATIONS */ #define XOR(a, b) CHECK(CAT(CAT(XOR_, a), b)) #define XOR_10 PROBE(1) #define XOR_01 PROBE(1) #define AND(a, b) CHECK(CAT(CAT(AND_, a), b)) #define AND_11 PROBE(1) #define OR(a, b) CHECK(CAT(CAT(OR_, a), b)) #define OR_01 PROBE(1) #define OR_10 PROBE(1) #define OR_11 PROBE(1) /* 0 => 1, 1 => 0 */ #define COMP(BIT) CAT(COMP_, BIT) #define COMP_0 1 #define COMP_1 0 /* END OF BOOLEAN OPERATIONS */ /* * DECIMAL OPERATIONS */ #define DEC_INC(a) CAT(DEC_INC_, a) #define DEC_INC_0 1 #define DEC_INC_1 2 #define DEC_INC_2 3 #define DEC_INC_3 4 #define DEC_INC_4 5 #define DEC_INC_5 6 #define DEC_INC_6 7 #define DEC_INC_7 8 #define DEC_INC_8 9 #define DEC_INC_9 0 #define DEC_EQUIV(a, b) CHECK(CAT(CAT(DEC_EQUIV_, a), b)) #define DEC_EQUIV_00 PROBE(1) #define DEC_EQUIV_11 PROBE(1) #define DEC_EQUIV_22 PROBE(1) #define DEC_EQUIV_33 PROBE(1) #define DEC_EQUIV_44 PROBE(1) #define DEC_EQUIV_55 PROBE(1) #define DEC_EQUIV_66 PROBE(1) #define DEC_EQUIV_77 PROBE(1) #define DEC_EQUIV_88 PROBE(1) #define DEC_EQUIV_99 PROBE(1) /* END OF DECIMAL OPERATIONS */ /* Basically, BOOL(x) := !!x */ #define BOOL(x) COMP(NOT(x)) #define IF(N, ...) IIF(BOOL(N)) #define WHEN(N) IF(N)(EXPAND, EAT) #define EXPAND_TEST_EXISTS(...) GOOD, EXISTS(__VA_ARGS__) ) EAT ( #define DO_EXPAND_TEST_EXISTS(x) (CAT(EXPAND_TEST_, x), DOESNT_EXIST) #define GET_TEST_EXISTS_VALUE_(_, value) value #define GET_TEST_EXISTS_VALUE(x) GET_TEST_EXISTS_VALUE_ x #define TEST_EXISTS(x) GET_TEST_EXISTS_VALUE ( DO_EXPAND_TEST_EXISTS (x) ) TEST(EXISTS) ( EXISTS(FOO) TEST_EXISTS(EXISTS(FOO)) DOESNT_EXIST TEST_EXISTS(FOO) ) #define EXTRACT_VALUE(exist_value) CAT(EXTRACT_VALUE_, exist_value) #define EXTRACT_VALUE_EXISTS(...) __VA_ARGS__ #define CONVERT_EXISTS_TO_BOOL(value) CAT(CONVERT_EXISTS_TO_BOOL_, value) #define CONVERT_EXISTS_TO_BOOL_EXISTS(...) 1 #define CONVERT_EXISTS_TO_BOOL_DOESNT_EXIST 0 #define TRY_EXTRACT_EXISTS(value, ...) \ IF(CONVERT_EXISTS_TO_BOOL(TEST_EXISTS(value))) \ (EXTRACT_VALUE(value), __VA_ARGS__) TEST(TRY_EXTRACT_EXISTS) ( FOO TRY_EXTRACT_EXISTS(EXISTS(FOO), DEFAULT) DEFUALT TRY_EXTRACT_EXISTS(FOO, DEFAULT) ) /* * We are going to represent a number by list of digits, e.g. * * 1 => (1, ) * 13 => (3, 1) * * Let's define some list operations. */ #define HEAD(head, ...) head #define TAIL(head, ...) __VA_ARGS__ #define ENCLOSE(...) ( __VA_ARGS__ ) #define EXPLODE_(...) __VA_ARGS__ #define EXPLODE(...) EXPLODE_ __VA_ARGS__ #define EXPLODE_INDIRECT() EXPLODE_ #define IS_LIST_EMPTY(...) \ TRY_EXTRACT_EXISTS( \ DEFER_0(HEAD) (__VA_ARGS__ EXISTS(1)), \ 0) TEST(IS_LIST_EMPTY) ( 1 IS_LIST_EMPTY() 0 IS_LIST_EMPTY(0) 0 IS_LIST_EMPTY(0, 0) ) #define EMPTY_LIST_TO_ZERO(...) \ IF (IS_LIST_EMPTY(__VA_ARGS__)) ( \ (0, ), \ (__VA_ARGS__)) /* * Now, let's define INCrease function, where, * * INC LIST_REPR(N) = LIST_REPR(N + 1) * * E.g. * * INC(1, ) = (2, ) * INC(9, ) = (0, 1) */ #define INC_INDIRECT() INC_NO_EVAL #define TRY_CARRY(x) CHECK(CAT(TRY_CARRY_, x), x) #define TRY_CARRY_DEC_INC_ PROBE(~) #define INC_NO_EVAL(head, ...) \ DEFER_1(EXPLODE_INDIRECT) () \ IF (DEC_INC(head)) ( \ (TRY_CARRY(DEC_INC(head)), __VA_ARGS__), \ (0, DEFER_2(INC_INDIRECT) () (__VA_ARGS__)) \ ) #define INC(...) (INNER_EVAL(INC_NO_EVAL(__VA_ARGS__))) TEST(INC) ( (1, ) INC(0) (2, ) INC(1) (0, 2) INC(9, 1) /* * Oops, this is actually (0, 0, EXPLODE_INDIRECT () (1, )) * Can't count to 100 Orz... * possible fix is to make INNER_EVAL evaluates more times. */ (0, 0, 1) INC(9, 9) ) /* * Apply @func_before and @func_after to each elements of a list. */ #define FOR_EACH_INDIRECT() FOR_EACH #define FOR_EACH(func_before, func_after, ...) \ WHEN (NOT(IS_LIST_EMPTY(__VA_ARGS__))) ( \ DEFER_1(func_before) (HEAD(__VA_ARGS__)) \ DEFER_1(FOR_EACH_INDIRECT) () ( \ func_before, func_after, TAIL(__VA_ARGS__) \ ) \ DEFER_1(func_after) (HEAD(__VA_ARGS__)) \ ) TEST(FOR_EACH) ( /* PRINT(1) PRINT(2) PRINT(3) PRINT(4) */ EVAL_7(FOR_EACH(PRINT, EAT, 1, 2, 3, 4)) /* PRINT(4) PRINT(3) PRINT(2) PRINT(1) */ EVAL_7(FOR_EACH(EAT, PRINT, 1, 2, 3, 4)) ) #define BOTH_EMPTY(list_a, list_b) \ AND(IS_LIST_EMPTY list_a, IS_LIST_EMPTY list_b) TEST(BOTH_EMPTY) ( 1 BOTH_EMPTY( ( ), ( ) ) 0 BOTH_EMPTY( (1), ( ) ) 0 BOTH_EMPTY( ( ), (1) ) 0 BOTH_EMPTY( (1), (1) ) ) #define IS_HEAD_EQUAL(list_a, list_b) \ DEC_EQUIV ( HEAD list_a, HEAD list_b ) TEST(IS_HEAD_EQUAL) ( 0 IS_HEAD_EQUAL( ( ), ( ) ) 0 IS_HEAD_EQUAL( (1), ( ) ) 0 IS_HEAD_EQUAL( ( ), (1, 1) ) 1 IS_HEAD_EQUAL( (1), (1) ) 0 IS_HEAD_EQUAL( (1), (0) ) 1 IS_HEAD_EQUAL( (1), (1, 0) ) ) #define IS_LIST_EQUAL_INDIRECT() IS_LIST_EQUAL_NO_EVAL #define IS_LIST_EQUAL_NO_EVAL(a, b) \ IF( BOTH_EMPTY( a, b ) ) ( \ 1, \ /* else */ \ IF( IS_HEAD_EQUAL(a, b) ) ( \ DEFER_2(IS_LIST_EQUAL_INDIRECT) () ((TAIL a), (TAIL b)), \ 0) \ ) #define IS_LIST_EQUAL(a, b) INNER_EVAL(IS_LIST_EQUAL_NO_EVAL(a, b)) #define IS_LIST_NOT_EQUAL(a, b) NOT(IS_LIST_EQUAL(a, b)) TEST(IS_LIST_EQUAL) ( 1 NOT(IS_LIST_EQUAL((1, 2), (1, 3))) 1 IS_LIST_NOT_EQUAL((1, 2), (1, 3)) 0 IS_LIST_NOT_EQUAL((0, 1), (0, 1)) 1 IS_LIST_NOT_EQUAL((0, 1), (1)) 1 IS_LIST_NOT_EQUAL((), (1)) 1 IS_LIST_NOT_EQUAL((1, 0, 1), (1, 0, 0, 1)) ) #define FOLD_INDIRECT() FOLD_NO_EVAL #define FOLD_NO_EVAL(func, list, init) \ IF ( IS_LIST_EMPTY list) ( \ init, \ DEFER_1(FOLD_INDIRECT) () (func, (TAIL list), func(init, HEAD list)) \ ) #define FOLD(func, list, init) INNER_EVAL(FOLD_NO_EVAL(func, list, init)) #define TAC(x, y) CAT(y, x) #define TO_INT(list) CAT(, FOLD(TAC, list, )) TEST(TO_INT) ( 102 TO_INT(INC(1, 0, 1)) ) #define IS_LIST_NOT_EQUAL_() IS_LIST_NOT_EQUAL #define FOR_LOOP_INDIRECT() FOR_LOOP_NO_EVAL #define FOR_LOOP_NO_EVAL(index, max, macro, ...) \ WHEN ( IS_LIST_NOT_EQUAL (index, max) ) ( \ DEFER_1(macro) (index, __VA_ARGS__) \ FOR_LOOP_INDIRECT EMPTY EMPTY () () () ( \ ENCLOSE( EXPLODE( DEFER_1(INC) index ) ), \ max, \ macro, \ __VA_ARGS__ \ ) \ ) #define FOR_LOOP(...) EVAL_2(EVAL_1(EVAL_1(FOR_LOOP_NO_EVAL(__VA_ARGS__)))) #define PRINT(list_b, list_a) \ printf(PRINT_FORMAT, \ TO_INT (list_a), \ TO_INT (list_b), \ (TO_INT (list_a)) * (TO_INT (list_b))); #define INNER_LOOP(x, ...) \ FOR_LOOP_NO_EVAL(START, END, PRINT, x) \ printf("\n"); #ifndef DEBUG #include int main() { EVAL_7(FOR_LOOP(START, END, INNER_LOOP)) } #endif