recursion method inside ruby minesweeper game stack level too deep - ruby

Question

I am triggering endless recursion when trying to make a method that pulls up tiles when they are a zero. I have been testing by entering the following in irb:
class Board
attr_accessor :size, :board
def initialize(size = gets.chomp.to_i)
#size = size
#board = (1..#size).map { |x| ["L"] * #size }
end
def print_board
#board.map { |row| puts row.join }
end
end
class Mine
attr_accessor :proxi, :row, :col
def initialize(proxi)
#proxi = proxi
#row = 0
#col = 0
#random = Random.new
check_position
end
def check_position
if #proxi.board[#row - 1][#col - 1] != "L"
#row = #random.rand(1..#proxi.board.length)
#col = #random.rand(1..#proxi.board[0].length)
check_position
else
map_position
end
end
def map_position
#proxi.board[#row - 1][#col - 1] = "*"
end
end
b = Board.new(20)
m = (1..b.size * 2).map { |i| i = Mine.new(b) }
class Detector
attr_accessor :board, :proxi, :row, :col, :value
def initialize(board, proxi)
#board = board
#proxi = proxi
#row = 0
#col = 0
#value = 0
end
def mine?
if #proxi.board[#row - 1][#col - 1] == "*"
true
else
false
end
end
def detect
(#row - 1..#row + 1).each do |r|
(#col - 1..#col + 1).each do |c|
unless (r - 1 < 0 || r - 1 > #proxi.size - 1) || (c - 1 < 0 || c - 1 > #proxi.size - 1)
#value += 1 if #proxi.board[r - 1][c - 1] == "*"
end
end
end
end
def map_position
#proxi.board[#row - 1][#col - 1] = #value
#board.board[#row - 1][#col - 1] = #value
end
def recursion
if #proxi.board[#row - 1][#col - 1] == 0
(#row - 1..#row + 1).each do |r|
(#col - 1..#col + 1).each do |c|
unless (r - 1 < 0 || r - 1 > #proxi.size - 1) || (c - 1 < 0 || c - 1 > #proxi.size - 1)
#row, #col = r, c
detect
map_position
recursion
end
end
end
end
end
def reset
#row, #col, #value = 0, 0, 0
end
end
d = Detector.new(b, b)
b.print_board
If the output has plenty of free space in the upper right corner proceed to pasting the next part, else repaste.
d.row = 1
d.col = 1
d.mine?
d.detect
d.map_position
d.recursion
b.print_board
It will error out with a stack level too deep error at the recursion method. I know this is because it is having issues ending the recursive pattern. I thought my two unless statements deterring it from searching off the board would limit it to the area in the board. Plus the mines would force it to be limited in zeros it can expose. Maybe it is somehow writing spaces off the board or overwriting things on the board?

Answer 1

You don’t need a recursion here. Simply check each position for mines around:
Please always use 0-based arrays to eliminate lots of #blah - 1.
In detect you need to return immediately if there is a mine and set the #value otherwise:
def detect
return if #proxi.board[#row][#col] == '*'
value = 0 # no need to be global anymore
(#row - 1..#row + 1).each do |r|
(#col - 1..#col + 1).each do |c|
unless r < 0 || r >= #proxi.size || c < 0 || c >= #proxi.size
value += 1 if #proxi.board[r][c] == "*"
end
end
end
#proxi.board[#row][#col] = value
end
Now you don’t need map_position method at all. Simply check all the cells:
def check
(0..#proxi.size - 1).each do |r|
(0..#proxi.size - 1).each do |c|
#row, #col = r, c
detect
end
end
end
Hope it helps.

Answer 2

Exceeding the stack size is usually an indication that your recursion does not have the correct terminating condition. In your case, what mechanism is in place to prevent recursion from being called multiple times with the same #row #col pair? Note that of the 9 pairs that (#row - 1..#row + 1) (#col - 1..#col + 1) produce, one of those pairs is #row #col itself. The function will call itself infinitely many times!
A simple way to solve this would be to have something like a revealed array that keeps track of visited cells. Then recursion would mark each cell it visits as visited and return immediately if it is called on an already visited cell.
Additionally, your use of instance variables is extremely fragile here. Recursion relies on the fact that each function call has its own scope, but every call of recursion shares the same instance variables - which you're using to pass arguments! You should be using method arguments to keep the scopes distinct.