Clean up unused public functions

Author: yizhe

positions.py

@@ -6,26 +6,13 @@
 from vision import SquareType
 
 
-Square = namedtuple("Square", ["x", "y"])
-SquarePair = namedtuple("SquarePair", ["start", "end"])
-
-
 def print_position(position):
     for x in range(8):
         for y in range(8):
             print(position[x][y], sep="", end="")
         print()
 
 
-# Convert a move(point pair) to algebraic notation.
-def pair_to_algebraic(pair):
-    def square_to_string(square):
-        mapping = "abcdefgh"
-        return mapping[square.y] + str(8 - square.x)
-
-    return square_to_string(pair.start) + square_to_string(pair.end)
-
-
 # Extracts position from a chess.Board.
 def get_position(board):
     mapping = {
@@ -68,79 +55,89 @@ def type_of(x):
     return [[type_of(lst[i * 8 + j]) for j in range(8)] for i in range(8)]
 
 
-# Returns a move(point pair) by analysing differences between two positions.
-# A position is an 8x8 array of SquareType.
-def diff_position(old_position, new_position):
-    diff = [
-        Square(x, y)
-        for x in range(8)
-        for y in range(8)
-        if old_position[x][y] != new_position[x][y]
-    ]
-
-    # Number of differences between boards:
-    # Castling has 4.
-    # Capture en passant has 3.
-    # Any other move, promotion, or normal capture has 2.
-    if len(diff) == 4:
-        # Castling
-        king_points = [p for p in diff if p.y == 4]
-        rook_points = [p for p in diff if p.y == 0 or p.y == 7]
-        if len(king_points) != 1 or len(rook_points) != 1:
-            raise IllegalMoveError
-
-        p = king_points[0]
-        q = rook_points[0]
-        if q.y == 0:
-            # Castle long
-            return SquarePair(p, Square(p.x, 2))
-        elif q.y == 7:
-            # Castle short
-            return SquarePair(p, Square(p.x, 6))
-        else:
-            raise Exception("")
-
-    elif len(diff) == 3:
-        # Capture en passant
-        pawn_points = [
-            p for p in diff if new_position[p.x][p.y] != SquareType.empty
-        ]
-        if len(pawn_points) != 1:
-            raise IllegalMoveError
-
-        p = pawn_points[0]
-        start_points = [
-            q
-            for q in diff
-            if q != p and old_position[q.x][q.y] == new_position[p.x][p.y]
+# Returns a chess.Move object by analysing change of positions.
+# [board] should be the board of the [new_position]
+def get_move_from_diff(board, old_position, new_position):
+    # A SquarePair denotes the starting and ending point of a move.
+    Square = namedtuple("Square", ["x", "y"])
+    SquarePair = namedtuple("SquarePair", ["start", "end"])
+
+    # Convert a move(point pair) to algebraic notation.
+    def pair_to_algebraic(pair):
+        def square_to_string(square):
+            mapping = "abcdefgh"
+            return mapping[square.y] + str(8 - square.x)
+
+        return square_to_string(pair.start) + square_to_string(pair.end)
+
+    # Returns a move(point pair) by analysing differences between two positions.
+    def diff_position(old_position, new_position):
+        diff = [
+            Square(x, y)
+            for x in range(8)
+            for y in range(8)
+            if old_position[x][y] != new_position[x][y]
         ]
-        if len(start_points) != 1:
-            raise IllegalMoveError
 
-        return SquarePair(start_points[0], p)
-
-    elif len(diff) == 2:
-        # Normal move, capture, or promotion
-        start_points = [
-            p for p in diff if new_position[p.x][p.y] == SquareType.empty
-        ]
-        if len(start_points) != 1:
-            raise IllegalMoveError
-        start = start_points[0]
+        # Number of differences between boards:
+        # Castling has 4.
+        # Capture en passant has 3.
+        # Any other move, promotion, or normal capture has 2.
+        if len(diff) == 4:
+            # Castling
+            king_points = [p for p in diff if p.y == 4]
+            rook_points = [p for p in diff if p.y == 0 or p.y == 7]
+            if len(king_points) != 1 or len(rook_points) != 1:
+                raise IllegalMoveError
+
+            p = king_points[0]
+            q = rook_points[0]
+            if q.y == 0:
+                # Castle long
+                return SquarePair(p, Square(p.x, 2))
+            elif q.y == 7:
+                # Castle short
+                return SquarePair(p, Square(p.x, 6))
+            else:
+                raise Exception("")
+
+        elif len(diff) == 3:
+            # Capture en passant
+            pawn_points = [
+                p for p in diff if new_position[p.x][p.y] != SquareType.empty
+            ]
+            if len(pawn_points) != 1:
+                raise IllegalMoveError
+
+            p = pawn_points[0]
+            start_points = [
+                q
+                for q in diff
+                if q != p and old_position[q.x][q.y] == new_position[p.x][p.y]
+            ]
+            if len(start_points) != 1:
+                raise IllegalMoveError
+
+            return SquarePair(start_points[0], p)
+
+        elif len(diff) == 2:
+            # Normal move, capture, or promotion
+            start_points = [
+                p for p in diff if new_position[p.x][p.y] == SquareType.empty
+            ]
+            if len(start_points) != 1:
+                raise IllegalMoveError
+            start = start_points[0]
+
+            end_points = [p for p in diff if p != start]
+            if len(end_points) != 1:
+                raise IllegalMoveError
+            end = end_points[0]
+            return SquarePair(start, end)
 
-        end_points = [p for p in diff if p != start]
-        if len(end_points) != 1:
+        else:
             raise IllegalMoveError
-        end = end_points[0]
-        return SquarePair(start, end)
-
-    else:
-        raise IllegalMoveError
-
 
-# Returns a chess.Move object by analysing change of positions.
-# [board] should be the board of the [new_position]
-def get_move_from_diff(board, old_position, new_position):
     square_pair = diff_position(old_position, new_position)
     assert square_pair is not None