reformat and refactor a bit

include/pieces.h

@@ -7,6 +7,6 @@
 bool move_ok(const tile_t board[BOARD_SIZE],
              index_t      from,
              index_t      to,
-             int    player);
+             int          player);
 
 #endif

include/util.h

@@ -1,7 +1,7 @@
 #include "common.h"
 
 bool    tile_empty(tile_t t);
-index_t abs_pos(index_t p);
+index_t abs_index(index_t i);
 index_t column(index_t i);
 index_t row(index_t i);
 tile_t  abs_tile(tile_t t);

src/chess.c

@@ -5,30 +5,32 @@
 
 #include <ctype.h>  /* isalpha, isdigit ... */
 #include <locale.h> /* setlocale */
+#include <stdint.h> /* uint64_t */
 #include <stdio.h>  /* printf, scanf */
 #include <string.h> /* memcpy */
 
-int    do_turn(int turn_no, tile_t board[BOARD_SIZE]);
+#define CLEAR_SCREEN() printf("\033[2J")
+
+int     do_turn(int turn_no, tile_t board[BOARD_SIZE]);
 void    init_board(tile_t board[BOARD_SIZE]);
 index_t input_to_index(char input[2]);
 
 int main()
 {
-    int turn = 0;
-
     setlocale(LC_ALL, "C.UTF-8");
 
-    tile_t board[8 * 8] = { 0 };
+    tile_t board[BOARD_SIZE] = { 0 };
 
     init_board(board);
 
+    int turn = 0;
+
     while (true) {
-        printf("\033[2J"); // clear screen
+        CLEAR_SCREEN();
         print_board(board);
 
-		// turn increments on valid inputs,
+        // turn increments on valid inputs,
-		// otherwise refreshes screen
+        turn += do_turn(turn, board);
-        turn = do_turn(turn, board);
     }
 
     return 0;
@@ -59,7 +61,7 @@ void init_board(tile_t board[BOARD_SIZE])
  * \param turn_no Turn number
  * \param board   Pointer to list of tiles representing board state
  *
- * \return turn+1 if successful, turn+0 if invalid input from player
+ * \return (int)1 if successful, (int)0 if invalid input from player
  * */
 int do_turn(int turn_no, tile_t board[BOARD_SIZE])
 {
@@ -68,31 +70,31 @@ int do_turn(int turn_no, tile_t board[BOARD_SIZE])
     int from = -1, to = -1;
 
     printf("\nPlayer %i, your turn to move", 1 + turn_no % 2);
-	printf("\nMove piece\nfrom: ");
+    printf("\nMove piece\nfrom: ");
 
-	scanf(" %2s", input);
+    scanf(" %2s", input);
 
-	from = input_to_index(input);
+    from = input_to_index(input);
 
-	if (from == -1)
+    if (from == -1)
-		return turn_no;
+        return 0;
 
-	printf("\nto: ");
+    printf("\nto: ");
-	scanf(" %2s", input);
+    scanf(" %2s", input);
 
-	to = input_to_index(input);
+    to = input_to_index(input);
 
-	if (to == -1)
+    if (to == -1)
-		return turn_no;
+        return 0;
 
-	if (! move_ok(board, from, to, turn_no % 2 ? BLACK : WHITE))
+    if (! move_ok(board, from, to, turn_no % 2 ? BLACK : WHITE))
-		return turn_no;
+        return 0;
 
     board[to]   = board[from];
     board[from] = E;
 
-	/* increment to make it next turn */
+    /* increment to make it next turn */
-	return turn_no+1;
+    return 1;
 }
 
 /**
@@ -100,21 +102,22 @@ int do_turn(int turn_no, tile_t board[BOARD_SIZE])
  *
  *	\param input string of length 2 representing tile, e.g. "A3"
  *
+ *	\return index value on valid input, -1 on invalid input
+ *
  * */
 index_t input_to_index(char input[2])
 {
-    int x = -1, y = -1, c;
+    int x = -1, y = -1;
 
     for (int i = 0; i < 2; i++) {
-        c = input[i];
+        const char c = input[i];
 
-        if (isalpha(c))
+        const char v = isalpha(c) ? toupper(c) : c;
-            c = toupper(input[0]);
 
-        if ('A' <= c && c <= 'H')
+        if ('A' <= v && v <= 'H')
-            x = c - 'A';
+            x = v - 'A';
-        else if ('1' <= c && c <= '8')
+        else if ('1' <= v && v <= '8')
-            y = c - '1';
+            y = v - '1';
     }
 
     if (x != -1 && y != -1)

src/pieces.c

@@ -2,31 +2,27 @@
 #include "common.h"
 #include "util.h"
 
- bool
+bool bishop_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to);
-bishop_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to);
+bool cardinal_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to);
- bool
+bool diagonal_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to);
-cardinal_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to);
+bool king_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to);
- bool
+bool knight_move_ok(index_t from, index_t to);
-diagonal_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to);
+bool pawn_move_ok(const tile_t board[BOARD_SIZE],
- bool
+                  index_t      from,
-king_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to);
+                  index_t      to,
- bool knight_move_ok(index_t from, index_t to);
+                  int          player);
- bool pawn_move_ok(const tile_t board[BOARD_SIZE],
+bool queen_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to);
-                         index_t      from,
+bool rook_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to);
-                         index_t      to,
-                         int          player);
- bool
-queen_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to);
- bool
-rook_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to);
 
 /**
- * Returns true if move is a valid pawn move
+ * Check if move is a valid pawn move
  *
- *  \param board  Array of tiles representing chess board state
+ * \param board  Array of tiles representing chess board state
- *  \param from   Index of board piece starts at
+ * \param from   Index of board piece starts at
- *  \param to     Index of board piece wants to move to
+ * \param to     Index of board piece wants to move to
- *  \param player Player to move
+ * \param player Player to move
+ *
+ * \return true if move is valid, false otherwise
  */
 bool pawn_move_ok(const tile_t board[BOARD_SIZE],
                   index_t      from,
@@ -53,22 +49,24 @@ bool pawn_move_ok(const tile_t board[BOARD_SIZE],
 }
 
 /**
- * Returns true if `to` is on a diagonal line of `from`, false otherwise
+ * Check if `to` is on a diagonal line of `from`
  *
  *  \param board Array of tiles representing chess board state
  *  \param from  Index of board piece is at
  *  \param to    Index of board piece tries to move to
+ *
+ * \return true if \p to is on a diagonal line of \p from
  */
 bool diagonal_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to)
 {
     const index_t col_diff = column(to) - column(from);
     const index_t row_diff = row(to) - row(from);
 
-    const index_t x_step = col_diff / abs_pos(col_diff);
+    const index_t x_step = col_diff / abs_index(col_diff);
-    const index_t y_step = ROW * row_diff / abs_pos(row_diff);
+    const index_t y_step = ROW * row_diff / abs_index(row_diff);
     const index_t step   = x_step + y_step;
 
-    if (abs_pos(col_diff) != abs_pos(row_diff))
+    if (abs_index(col_diff) != abs_index(row_diff))
         return false;
 
     for (index_t p = from + step; p != to; p += step)
@@ -79,23 +77,24 @@ bool diagonal_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to)
 }
 
 /**
- * Returns true if index `to` is on a cardinal line of `from`, false otherwise
+ * Check if index `to` is on a cardinal line of `from`
  *
  *  \param board Array of tiles representing chess board state
  *  \param from  Index of board piece is at
  *  \param to    Index of board piece tries to move to
+ *
+ * \return true if \p to and \p from share a column or row
  */
 bool cardinal_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to)
 {
     const index_t col_diff = column(to) - column(from);
-    const index_t row_diff = row(to) - row(from);
+    const index_t row_diff = row(to - from);
 
-    /* cardinal moves means one direction has to be zero */
     if (row_diff > 0 && col_diff > 0)
         return false;
 
-    index_t step = row_diff ? ROW * row_diff / abs_pos(row_diff) :
+    index_t step = row_diff ? ROW * row_diff / abs_index(row_diff) :
-                              col_diff / abs_pos(col_diff);
+                              col_diff / abs_index(col_diff);
 
     for (index_t p = from + step; p != to; p += step)
         if (! tile_empty(board[p]))
@@ -105,11 +104,13 @@ bool cardinal_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to)
 }
 
 /**
- * Returns true if move is a valid bishop move
+ * Check if move is a valid bishop move
  *
- *  \param board Array of tiles representing chess board state
+ * \param board Array of tiles representing chess board state
- *  \param from  Index of board piece is at
+ * \param from  Index of board piece is at
- *  \param to    Index of board piece tries to move to
+ * \param to    Index of board piece tries to move to
+ *
+ * \return true if move is valid, false otherwise
  */
 bool bishop_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to)
 {
@@ -117,11 +118,13 @@ bool bishop_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to)
 }
 
 /**
- * Returns true if move is a valid rook move
+ * Check if move is a valid rook move
  *
- *  \param board Array of tiles representing chess board state
+ * \param board Array of tiles representing chess board state
- *  \param from  Index of board piece is at
+ * \param from  Index of board piece is at
- *  \param to    Index of board piece tries to move to
+ * \param to    Index of board piece tries to move to
+ *
+ * \return true if move is valid, false otherwise
  */
 bool rook_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to)
 {
@@ -129,30 +132,34 @@ bool rook_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to)
 }
 
 /**
- * Returns true if move is a valid knight move
+ * Check if move is a valid knight move
  *
- *  \param from  Index of board piece is at
+ * \param from  Index of board piece is at
- *  \param to    Index of board piece tries to move to
+ * \param to    Index of board piece tries to move to
+ *
+ * \return true if move is valid, false otherwise
  */
 bool knight_move_ok(index_t from, index_t to)
 {
-    const index_t c = abs_pos(column(to) - column(from));
+    const index_t c = abs_index(column(to) - column(from));
-    const index_t r = abs_pos(row(to - from));
+    const index_t r = abs_index(row(to - from));
 
     return (c == 1 && r == 2) || (c == 2 && r == 1);
 }
 
 /**
- * Returns true if move is a valid king move
+ * Check if move is a valid king move
  *
  *  \param board Array of tiles representing chess board state
  *  \param from  Index of board piece is at
  *  \param to    Index of board piece tries to move to
+ *
+ * \return true if move is valid, false otherwise
  */
 bool king_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to)
 {
-    const index_t abs_col_diff = abs_pos(column(to) - column(from));
+    const index_t abs_col_diff = abs_index(column(to) - column(from));
-    const index_t abs_row_diff = abs_pos(row(to) - row(from));
+    const index_t abs_row_diff = abs_index(row(to) - row(from));
 
     (void)board;
 
@@ -160,11 +167,13 @@ bool king_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to)
 }
 
 /**
- * Returns true if move is a valid queen move
+ * Check if move is a valid queen move
  *
- *  \param board Array of tiles representing chess board state
+ * \param board Array of tiles representing chess board state
- *  \param from  Index of board piece is at
+ * \param from  Index of board piece is at
- *  \param to    Index of board piece tries to move to
+ * \param to    Index of board piece tries to move to
+ *
+ * \return true if move is valid, false otherwise
  */
 bool queen_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to)
 {
@@ -173,12 +182,14 @@ bool queen_move_ok(const tile_t board[BOARD_SIZE], index_t from, index_t to)
 }
 
 /**
- * Returns true if a move is valid, false otherwise
+ * Check if a move is valid
  *
  * \param board  Pointer to list of tiles representing board state
  * \param from   Tile to move piece from
  * \param to     Tile to move piece to
  * \param player The current player to move
+ *
+ * \return true if move is valid, false otherwise
  * */
 bool move_ok(const tile_t board[BOARD_SIZE],
              index_t      from,

src/util.c

@@ -2,22 +2,26 @@
 #include "util.h"
 
 /**
- * Returns the absolute value of an index_t value
+ * Calculate the absolute value of an index_t value
  *
  * \param p positive or negative index_t
+ *
+ * \return the absolute value of p
  */
-index_t abs_pos(index_t p)
+index_t abs_index(index_t i)
 {
-    if (p < 0)
+    if (i < 0)
-        return -1 * p;
+        return -1 * i;
 
-    return p;
+    return i;
 }
 
 /**
- * Returns the absolute value of a tile_t value
+ * Calculate the absolute value of a tile_t value
  *
  * \param t positive or negative tile_t
+ *
+ * \return the absolute value of t
  * */
 tile_t abs_tile(tile_t t)
 {
@@ -28,9 +32,11 @@ tile_t abs_tile(tile_t t)
 }
 
 /**
- * Returns true if tile is empty, false otherwise
+ * Check if tile is has no piece on it
  *
- *	\param t tile to check if empty
+ * \param t tile to check if empty
+ *
+ * \return true if tile is empty, false otherwise
  * */
 bool tile_empty(tile_t t)
 {
@@ -38,9 +44,11 @@ bool tile_empty(tile_t t)
 }
 
 /**
- * Returns row number of 1D board index
+ * Get row of index
  *
  * \param i index to get row number of
+ *
+ * \return row number of i
  * */
 index_t row(index_t i)
 {
@@ -48,9 +56,11 @@ index_t row(index_t i)
 }
 
 /**
- * Returns column number of board index
+ * Get column of index
  *
  * \param i index to get column number of
+ *
+ * \return column number of i
  * */
 index_t column(index_t i)
 {
@@ -58,10 +68,12 @@ index_t column(index_t i)
 }
 
 /**
- * Returns true if a and b are tiles of opposite color, false otherwise
+ * Check if two tiles have pieces of the opposite color
  *
  * \param a Tile to compare
  * \param b Tile to compare it with
+ *
+ * \return true if a and b are opposite colors, false otherwise
  * */
 bool opposite_color(tile_t a, tile_t b)
 {
@@ -69,10 +81,12 @@ bool opposite_color(tile_t a, tile_t b)
 }
 
 /**
- * Returns true if a and b are pieces of the same color, false otherwise
+ * Check if two tiles have pieces of the same color
  *
  * \param a Tile to compare
  * \param b Tile to compare it with
+ *
+ * \return true if a and b are opposite colors, false otherwise
  * */
 bool same_color(tile_t a, tile_t b)
 {