Number base conversion

base_converter.rb

# Converts from base 10 to a different base

def get_digit(digit)
  digit.to_i > 9 ? sprintf("%0X",digit.to_i) : digit.to_s
end

def to_base(input,new_base)
  raise "Number base should be between 2 and 16!" if ((new_base > 16) || (new_base < 2))
  raise "Input number must be an unsigned integer!" if (input < 0)  
  return 0 if input == 0
  
  output = ''
  current = input
  max = Math.log(current)/Math.log(new_base)
  max = max.truncate
  pow = max
  
  index = max
  while index >= 0 do
    digit = current / (new_base ** index)
    
    if (digit >= new_base)
      raise "Digit must be between 0 and #{new_base-1} for numbers in base #{new_base}" 
    end
    
    character = sprintf("%X",digit.to_i)    
    output << character
    #current = input % (digit*(new_base ** pow)) if digit>0
    current = current - (digit*(new_base ** index))  
    index = index - 1
  end
  return output
end

# Test
# 202000001112112 b3 = 10629941 b10
def from_base(input,base)
  output = 0
  index = 0
  while index <= input.to_s.length-1 do
    character = input.to_s[index..index]    
    if (character !~ /[0-9A-Za-z]/)    
      raise "Illegal digit found '#{character}' in '#{input}!"
    end
    
    digit = (character =~ /[A-Za-z]/) ? sprintf("%d","0x#{character}").to_i : character.to_i
    if (digit >= base)    
      raise "Digits must be between 0 and #{base-1} for numbers in base #{base}" 
    end
    
    power  = (input.to_s.length - 1) - index
    value  = digit * (base ** power)
    output = output + value
    index  = index + 1
  end
  return output
end

# Add new to_i() to class String
class String  
  def to_d(base)
    from_base(to_s,base)
  end
end