Converting simple code from python to ruby

Question

I have the following code on python:

f = open("configuration.txt", "r")
position = {}
counter = 0
with open("configuration.txt") as fileobj:
    for line in fileobj:
        for ch in line:
            if ch.isdigit():
                position[int(ch)] = counter
        counter+=1
# print(dict(sorted(position.items())))

position = dict(sorted(position.items()))
diskPositions = list(position.values())

disk = {0:'4',1:'3',2:'2',3:'1'}
pegs = {0:'A',1:'B',2:'C'}
# print(position)
def moveDisks(diskPositions, largestToMove, targetPeg):
    for badDisk in range(largestToMove, len(diskPositions)):
        currentPeg = diskPositions[badDisk]
        if diskPositions[badDisk] != targetPeg:
            otherPeg = 3 - targetPeg - currentPeg
            moveDisks(diskPositions, badDisk + 1, otherPeg)
            print(disk[badDisk], "-", pegs[targetPeg])
            diskPositions[badDisk] = targetPeg
            moveDisks(diskPositions, badDisk + 1, targetPeg)
            break;

moveDisks(diskPositions[::-1], 0, 2)

And I need to convert this code into ruby. I started doing it, but I'm stuck and don't know where is the error, or what I'm doing different.

When I runt it, i receive the following error on line 30, caused by a nil variable:

/hanoi/final.rb:30:in `-': nil can't be coerced into Integer (TypeError)```

Ruby Code :

f = open("configuration.txt", "r")
position = {}
counter = 0

def is_digit(look_ahead)
  look_ahead =~ /[[:digit:]]/
end

File.open('configuration.txt', 'r') do |f|
  f.each_line do |l| # iterate on each character
    l.each_char do |c|
      if is_digit(c)
        position[c.to_i] = counter
      end
    end
    counter+=1
  end
end

position = position.sort.to_h
disk_positions = position.values

disk = {0 => '4', 1 => '3', 2 => '2', 3 => '1'}
pegs = {0 => 'A', 1 => 'B', 2 => 'C'}

def moveDisks(diskPositions, largestToMove, targetPeg)
  for badDisk in (largestToMove..diskPositions.length)
    currentPeg = diskPositions[badDisk]
    if diskPositions[badDisk] != targetPeg
      otherPeg = 3 - targetPeg - currentPeg
      moveDisks(diskPositions, badDisk + 1, otherPeg)
      print disk[badDisk].to_s + "-", pegs[targetPeg].to_s
      diskPositions[badDisk] = targetPeg
      moveDisks(diskPositions, badDisk + 1, targetPeg)
      break
    end
  end
end

moveDisks(disk_positions.reverse, 0, 2)

PS: configuration.txt is a text file containing the following lines:

A-1
B-4:2
C-3

Answer 1

In Python, the built-in range function is not inclusive, so it doesn't return the last number. Ruby doesn't use a function, it has a couple of operators - the two-dot form .. creates a range including the last number, and the three-dot form ... which excludes the high value. See the documentation for more information.

Your posted code has a few additional errors and isn't very idiomatic, but your error is being caused by using the inclusive form, which results in a nil value being returned when the index goes out of bounds. The range (largestToMove...diskPositions.length) would be the equivalent for the Python function.