Awesome C Syntax

**SuchtyTV** · 08-08-2019

If you look at this code, everythink works just fine.

Code:

int filter_all_legal_moves(BOARD_STATE* pboard_state, MOVE_DATA* pmove_data){	//check all moves
	for(int i = 0; i < pmove_data->used_array_size; i++){
		BOARD_STATE bstate = make_move_with_copy(pboard_state, pmove_data->moves[i]);
		MOVE_DATA new_move_data = return_all_moves(&bstate, 0);
		if(can_king_be_killed(&bstate, &new_move_data)){
			pmove_data->moves[i] = "\0\0";
		}
	}
	int i = -1;
	int p = -1;
	while(1){
		i++;
		do ++p; while(p < pmove_data->used_array_size && pmove_data->moves[p] == "\0\0");
		if (p >= pmove_data->array_size) break;
		pmove_data->moves[i] = pmove_data->moves[p];


	}
	pmove_data->used_array_size = i;
	//check e.p
	//check castling
	return 1;
}

Now let us write the code like this:

Code:

int filter_all_legal_moves(BOARD_STATE* pboard_state, MOVE_DATA* pmove_data){	//check all moves
	for(int i = 0; i < pmove_data->used_array_size; i++){
		BOARD_STATE bstate = make_move_with_copy(pboard_state, pmove_data->moves[i]);
		MOVE_DATA new_move_data = return_all_moves(&bstate, 0);
		if(can_king_be_killed(&bstate, &new_move_data)){
			pmove_data->moves[i] = "\0\0";
		}
	}
	int i, p = -1;
	while(1){
		i++;
		do ++p; while(p < pmove_data->used_array_size && pmove_data->moves[p] == "\0\0");
		if (p >= pmove_data->array_size) break;
		pmove_data->moves[i] = pmove_data->moves[p];


	}
	pmove_data->used_array_size = i;
	//check e.p
	//check castling
	return 1;
}

The debugger tells me i = 7 after initalization...
Why?

**laserlight** · 08-08-2019

In the second example, you declared i but did not initialise it, so it was given a garbage initial value. You probably wanted to write:

Code:

int i = -1, p = -1;

**Salem** · 08-08-2019

> pmove_data->moves[i] = "\0\0"
...
> pmove_data->moves[p] == "\0\0"
This isn't guaranteed to work, and it isn't how you compare strings.

It is common for compilers to combine identical string constants, such that say this

Code:

if ( "hello" == "hello" ) {
  // string constants merged
} else {
  // string constants not merged
}

will usually result in true rather than false.

You need a singular char pointer which is otherwise unused elsewhere in your program, eg.

Code:

char dummy[];

//....
int filter_all_legal_moves(BOARD_STATE* pboard_state, MOVE_DATA* pmove_data){   //check all moves
    for(int i = 0; i < pmove_data->used_array_size; i++){
        BOARD_STATE bstate = make_move_with_copy(pboard_state, pmove_data->moves[i]);
        MOVE_DATA new_move_data = return_all_moves(&bstate, 0);
        if(can_king_be_killed(&bstate, &new_move_data)){
            pmove_data->moves[i] = dummy;
        }
    }
    int i = -1;
    int p = -1;
    while(1){
        i++;
        do ++p; while(p < pmove_data->used_array_size && pmove_data->moves[p] == dummy);
        if (p >= pmove_data->array_size) break;
        pmove_data->moves[i] = pmove_data->moves[p];
 
 
    }
    pmove_data->used_array_size = i;
    //check e.p
    //check castling
    return 1;
}

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