Added license information!

18 files changed, 413 insertions, 71 deletions

diff --git a/include/actions.c b/include/actions.c
index 5085330..800a2d4 100644
--- a/include/actions.c
+++ b/include/actions.c
@@ -1,3 +1,20 @@
+/*
+	This file is part of ctak.
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 #include "actions.h"
 
 // ===================================================================
@@ -67,6 +84,7 @@ void action_list_init(void) {
 
 action_list_t *action_list_generate(void) {
 	action_list_t *list = malloc(sizeof(struct action_list_s));
+
 	// TODO: trap errno
 	list->length = 0;
 	list->head = NULL;
@@ -129,16 +147,22 @@ action_list_t *action_list_generate(void) {
 					 * For each direction, generate all possible ordered integer
 					 * partitions of 1 ≤ num ≤ count whose number of summands is
 					 * exactly 1 ≤ summands ≤ min(end_stops[dir], num) -- we
-					 * write summands as steps
+					 * write summands as steps.
+					 *
+					 * We exploit the `gaps' bijection here and elsewhere
+					 * between ordered {integer partitions of n with s summands}
+					 * and {binary strings of length n-1 with s-1 set bits}.
 					 */
 					for (enum MOVE_DIRECTION dir=M_UP; dir<=M_RIGHT; dir++) {
 						for (uint8_t num = 1; num <= count; num++) {
 							for (uint8_t steps = 1;
 									 steps <= end_stops[dir] && steps <= num;
 									 steps++) {
-								// TODO: Generalise to board_size!
-								uint8_t gaps = 0x07 >> (board_size-steps-1);
-								// 0b0000[0111] because 4-1=3 and 5-1=4
+								uint8_t gaps =
+									((1<<(board_size - 2)) - 1) >> (board_size-steps-1);
+								// For 5x5 this givess 0b0000[0XXX] where steps-1 of
+								// those X's are 1s (starting with LSB) because 4-1=3
+								// and 5-1=4
 								do  {
 									/*
 									 * We skip the partition if it calls for multiple
@@ -214,9 +238,12 @@ void action_take(const action_t action) {
 			}
 		}
 	} else {
-		 // not interested in whether we crushed, it will work out by
-		 // anyway because we overwrite the top stone type. See (*) later
-		 // for when we do need to know.
+		/*
+		 * See the discussion around line 135 for an explanation of the
+		 * encoding. Here we are not interested in whether we crushed, it
+		 * will work out by anyway because we overwrite the top stone
+		 * type. See (*) later for when we do need to know.
+		 */
 		const uint8_t gaps = A_GET_DATA0(action) & 0x7F,
 			num = A_GET_DATA1(action) & 0x0F, // unpack
 			dir = A_GET_DATA1(action) >> 4;
diff --git a/include/actions.h b/include/actions.h
index ced0315..a1c90cc 100644
--- a/include/actions.h
+++ b/include/actions.h
@@ -1,3 +1,20 @@
+/*
+	This file is part of ctak.
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 #ifndef ACTIONS_H
 #define ACTIONS_H
 
@@ -6,6 +23,10 @@
 
 #include <tak.h>
 
+// ===================================================================
+// Types
+// ===================================================================
+
 enum A_TYPE { A_PLACE, A_MOVE };
 
 typedef uint32_t action_t;
@@ -33,11 +54,20 @@ typedef struct action_list_s {
 	uint32_t length;
 } action_list_t;
 
+// ===================================================================
+// Variables
+// ===================================================================
+
 extern int8_t move_deltas[4];
 
+// ===================================================================
+// Methods
+// ===================================================================
+
 void action_list_init(void);
 void action_list_free(action_list_t *list);
 action_list_t *action_list_generate(void);
+
 int action_move_to_front(const action_t action, action_list_t *list);
 
 void action_take(const action_t action);
diff --git a/include/cnn1986.c b/include/cnn1986.c
index ada1766..d4f6ad6 100644
--- a/include/cnn1986.c
+++ b/include/cnn1986.c
@@ -1,3 +1,20 @@
+/*
+	This file is part of ctak.
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 #include "cnn1986.h"
 #include "weights.h"
 
diff --git a/include/cnn1986.h b/include/cnn1986.h
index c04a04e..fe3817a 100644
--- a/include/cnn1986.h
+++ b/include/cnn1986.h
@@ -1,3 +1,20 @@
+/*
+	This file is part of ctak.
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 #include <tak.h>
 
 float cnn1986_evaluate_black_win(void);
diff --git a/include/lcdlib.c b/include/lcdlib.c
index 0933b2c..c956d5c 100644
--- a/include/lcdlib.c
+++ b/include/lcdlib.c
@@ -1,3 +1,20 @@
+/*
+	This file is part of ctak.
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 #include "lcdlib.h"
 
 static char previous_lines[LCD_HEIGHT][LCD_WIDTH+1];
diff --git a/include/lcdlib.h b/include/lcdlib.h
index fd28a0e..192b3a4 100644
--- a/include/lcdlib.h
+++ b/include/lcdlib.h
@@ -1,19 +1,43 @@
+/*
+	This file is part of ctak.
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 #include <stdlib.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <string.h>
 
+// ===================================================================
+// Types
+// ===================================================================
+
 #define LCD_WIDTH  16
 #define LCD_HEIGHT 2
 
 enum LCD_WRITE_MODE { L_OVERWRITE, L_SCROLL };
 
+// ===================================================================
+// Methods
+// ===================================================================
+
 int lcd_begin(void);
 void lcd_end(void);
 void lcd_clear(void);
 
-void lcd_put_line(const enum LCD_WRITE_MODE mode,
-									const char *line);
+void lcd_put_line(const enum LCD_WRITE_MODE mode, const char *line);
 
 void lcd_printf_line(const enum LCD_WRITE_MODE mode,
 										 const char *format, ...);
diff --git a/include/negamax.c b/include/negamax.c
index 3db5867..cdcfcf9 100644
--- a/include/negamax.c
+++ b/include/negamax.c
@@ -1,7 +1,24 @@
+/*
+	This file is part of ctak.
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 #include "negamax.h"
 
 // ===================================================================
-// Globals
+// Variables
 // ===================================================================
 
 const float infty = 3.0;
@@ -9,52 +26,52 @@ char negamax_ptn[9];
 uint8_t negamax_search_depth = 3;
 
 // ===================================================================
-// Helpers
+// Helper declarations
 // ===================================================================
 
-static float
-negamax(const uint8_t cur_depth, float alpha, float beta,
+static float negamax(const uint8_t cur_depth, float alpha, float beta,
 				const float colour);
 
 // ===================================================================
-// α-β negamax using the cnn1986 evaluation function and transposition
-// tables using Zobrist hasing and a treap
+// Exported functions
 // ===================================================================
 
-void
-negamax_init(const uint8_t new_board_size) {
+void negamax_init(const uint8_t new_board_size) {
 	board_size = new_board_size;
 	action_list_init();
 	zobrist_init();
 	tt_init();
 }
 
-void
-negamax_free(void) {
+void negamax_free(void) {
 	zobrist_free();
 }
 
-float
-negamax_generate(void) {
+float negamax_generate(void) {
 	// We need to start with something outside of [-∞,∞] because those
 	// values are wins
 	const float safe_infty = infty + 1;
 
 	tt_init();
-	float result = negamax(negamax_search_depth,
-												 -safe_infty, safe_infty,
-												 (ply & 1) ? +1.0 : -1.0);
+	float result =
+		negamax(negamax_search_depth,
+						-safe_infty, safe_infty,
+						(ply & 1) ? +1.0 : -1.0);
 	tt_free();
 
 	return result;
 }
 
+// ===================================================================
+// α-β negamax using the cnn1986 evaluation function and transposition
+// tables using Zobrist hasing and a chaining hash table
+// ===================================================================
+
 static enum TT_FLAG flag;
 static enum WIN_TYPE w;
 
-static float
-negamax(const uint8_t cur_depth, float alpha, float beta,
-				const float colour) {
+static float negamax(const uint8_t cur_depth, float alpha, float beta,
+										 const float colour) {
 
 	uint64_t hash = zobrist_compute();
 	tt_entry_t *entry = tt_seek(hash);
diff --git a/include/negamax.h b/include/negamax.h
index b41871e..77461b8 100644
--- a/include/negamax.h
+++ b/include/negamax.h
@@ -1,30 +1,52 @@
+/*
+	This file is part of ctak.
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 #include <stdint.h>
 #include <math.h>
 
 #include <tak.h>
-
 #include <actions.h>
 #include <cnn1986.h>
 #include <tt_llcht.h>
-#include <xorshift64.h>
 #include <zobrist.h>
 
+// ===================================================================
+// Variables
+// ===================================================================
+
 extern const float infty;
 extern char negamax_ptn[9];
 extern uint8_t negamax_search_depth;
 
-extern inline void
-negamax_display_progress(const uint8_t, const uint32_t length);
+extern void negamax_display_progress(const uint8_t cur_depth,
+																		 const uint32_t length);
+
+// ===================================================================
+// Methods
+// ===================================================================
 
-void
-negamax_init(const uint8_t new_board_size);
+void negamax_init(const uint8_t new_board_size);
 
-void
-negamax_free(void);
+void negamax_free(void);
 
-// Do negamax to depth negamax_search_depth and return PTN of best move
-// in negamax_ptn, along with its value as the return. The
-// negamax_display_progress function is called on every new square at
-// the top level.
+/*
+ * Do α-β negamax with transposition tables and naïve move ordering to
+ * depth `negamax_search_depth' and store the PTN of best move in
+ * `negamax_ptn', and return its value. The `negamax_display_progress'
+ * function is called on every new square at the top level.
+ */
 float negamax_generate(void);
-extern uint8_t yes;
diff --git a/include/tak.c b/include/tak.c
index 6d07ea0..c9c761c 100644
--- a/include/tak.c
+++ b/include/tak.c
@@ -1,3 +1,20 @@
+/*
+	This file is part of ctak.
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 #include "tak.h"
 
 // ===================================================================
diff --git a/include/tak.h b/include/tak.h
index 135e4eb..8b40430 100644
--- a/include/tak.h
+++ b/include/tak.h
@@ -1,14 +1,32 @@
+/*
+	This file is part of ctak.
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 #ifndef TAK_H
 #define TAK_H
 
 #include <stdint.h>
 
+// ===================================================================
+// Types
+// ===================================================================
+
 enum E_RESULT {ACT_OK, ACT_ILLEGAL, ACT_OVERFLOW,
 	PTN_VALID, PTN_INVALID, GAME_END };
 
-// -------------------------------------------------------------------
-// State management
-
 enum COLOUR         { C_WHITE, C_BLACK };
 enum STONE_VARIANT  { STONE_FLAT, STONE_STANDING, STONE_CAPSTONE };
 enum MOVE_DIRECTION { M_UP, M_DOWN, M_LEFT, M_RIGHT };
@@ -27,6 +45,10 @@ typedef uint16_t colour_stack_t;
 #define COUNT_AT(l)         (celldat[(l)] >> NUM_SHIFT)
 #define THE_COORDS(col,row) ((col)+(row)*board_size)
 
+// ===================================================================
+// Variables
+// ===================================================================
+
 extern enum WIN_TYPE won;
 extern uint8_t board_size;
 extern data_t celldat[36];
@@ -34,6 +56,13 @@ extern colour_stack_t colours[36];
 extern enum COLOUR current_colour;
 extern uint8_t white_count, black_count, ply;
 
+// ===================================================================
+// Methods
+// ===================================================================
+
+// -------------------------------------------------------------------
+// Game state
+
 void reset_state(const uint8_t new_board_size);
 void next_ply(void);
 
diff --git a/include/tt_llcht.c b/include/tt_llcht.c
index 9cbf647..b898b23 100644
--- a/include/tt_llcht.c
+++ b/include/tt_llcht.c
@@ -1,3 +1,20 @@
+/*
+	This file is part of ctak.
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 #include "tt_llcht.h"
 
 // ===================================================================
@@ -11,10 +28,9 @@ static tt_entry_t *table[TT_LLCHT_SIZE+1];
 // Helper declarations
 // ===================================================================
 
-tt_entry_t *
-new_ll_node(const uint64_t key, const enum TT_FLAG flag,
-						const uint8_t depth, const float value,
-						const action_t action);
+tt_entry_t * new_ll_node(const uint64_t key, const enum TT_FLAG flag,
+												 const uint8_t depth, const float value,
+												 const action_t action);
 
 
 // ===================================================================
@@ -69,10 +85,9 @@ int tt_insert(const uint64_t key, const enum TT_FLAG flag,
 // Helper function implementations
 // ===================================================================
 
-tt_entry_t *
-new_ll_node(const uint64_t key, const enum TT_FLAG flag,
-						const uint8_t depth, const float value,
-						const action_t action) {
+tt_entry_t * new_ll_node(const uint64_t key, const enum TT_FLAG flag,
+												 const uint8_t depth, const float value,
+												 const action_t action) {
 	tt_entry_t *new = malloc(sizeof(struct tt_node_s));
 	// TODO: trap errno
 	new->key = key;
diff --git a/include/tt_llcht.h b/include/tt_llcht.h
index f9a7a78..90b4164 100644
--- a/include/tt_llcht.h
+++ b/include/tt_llcht.h
@@ -1,3 +1,20 @@
+/*
+	This file is part of ctak.
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 #ifndef TT_LLCHT_H
 #define TT_LLCHT_H
 
@@ -22,7 +39,7 @@ typedef struct tt_node_s {
 } tt_entry_t;
 
 // ===================================================================
-// Globals
+// Variables
 // ===================================================================
 
 #define TT_LLCHT_SIZE ((uint32_t)((1<<19) - 1))
diff --git a/include/weights.c b/include/weights.c
index 905eb41..812a2eb 100644
--- a/include/weights.c
+++ b/include/weights.c
@@ -1,3 +1,20 @@
+/*
+	This file is part of ctak.
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 #include "weights.h"
 
 const float conv2d_weights[KERN_NUM][KERN_SIZE][KERN_SIZE][KERN_CHAN] =
diff --git a/include/weights.h b/include/weights.h
index dd479e3..d6666e7 100644
--- a/include/weights.h
+++ b/include/weights.h
@@ -1,3 +1,20 @@
+/*
+	This file is part of ctak.
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 #define KERN_SIZE  3
 #define KERN_CHAN  6
 #define KERN_NUM   12
diff --git a/include/xorshift64.c b/include/xorshift64.c
index 516218a..fd2fb6e 100644
--- a/include/xorshift64.c
+++ b/include/xorshift64.c
@@ -1,3 +1,20 @@
+/*
+	This file is part of ctak.
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 #include "xorshift64.h"
 
 uint64_t xors = (uint64_t)0xBF58476D1CE4E5B9;
diff --git a/include/xorshift64.h b/include/xorshift64.h
index 62a0a4e..4509772 100644
--- a/include/xorshift64.h
+++ b/include/xorshift64.h
@@ -1,8 +1,25 @@
-#include <stdint.h>
+/*
+	This file is part of ctak.
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
 
 #ifndef XORSHIFT_H
 #define XORSHIFT_H
 
+#include <stdint.h>
+
 extern uint64_t xors;
 
 #define XORSHIFT64 { \
diff --git a/include/zobrist.c b/include/zobrist.c
index feff5fa..21a99af 100644
--- a/include/zobrist.c
+++ b/include/zobrist.c
@@ -1,25 +1,38 @@
-#include "zobrist.h"
+/*
+	This file is part of ctak.
 
-// ===================================================================
-// Globals
-// ===================================================================
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
 
-static uint64_t *zobrist;
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#include "zobrist.h"
 
 // ===================================================================
-// Helpers
+// Variables
 // ===================================================================
 
+static uint64_t *zobrist;
 
 // ===================================================================
 // Exported method implementations
 // ===================================================================
 
-int
-zobrist_init(void) {
+int zobrist_init(void) {
 	if (zobrist != NULL) return EXIT_FAILURE;
 
 	zobrist = malloc(sizeof(uint64_t)*board_size*board_size*(15*2*3));
+	// TODO: trap errno
+
 	for (int k=0; k<board_size*board_size*(15*2*3); k++) {
 		XORSHIFT64;
 		zobrist[k] = RANDOM64;
@@ -28,16 +41,14 @@ zobrist_init(void) {
 	return EXIT_SUCCESS;
 }
 
-void
-zobrist_free(void) {
+void zobrist_free(void) {
 	if (zobrist != NULL) {
 		free(zobrist);
 		zobrist = NULL;
 	}
 }
 
-uint64_t
-zobrist_compute(void) {
+uint64_t zobrist_compute(void) {
 	uint64_t hash = 0;
 	for (uint8_t l=0; l<board_size*board_size; l++) {
 		colour_stack_t c = colours[l];
diff --git a/include/zobrist.h b/include/zobrist.h
index cfc2941..2b1a9dd 100644
--- a/include/zobrist.h
+++ b/include/zobrist.h
@@ -1,12 +1,26 @@
+/*
+	This file is part of ctak.
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful, but
+	WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+	General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with Takwrap.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
 #include <xorshift64.h>
 #include <tak.h>
 #include <actions.h>
 
-void
-zobrist_free(void);
+void zobrist_free(void);
 
-int
-zobrist_init(void);
+int zobrist_init(void);
 
-uint64_t
-zobrist_compute(void);
+uint64_t zobrist_compute(void);