simple repl that shows binary string to decimal string conversion -- doing conversion by hand.

bin_to_dec.rb

#!/usr/bin/env ruby

OUTPUT_FORMAT = "%s in decimal is %s"
ERROR_FORMAT  = "Argument %s must be a binary string (0 and 1 only)."



def convert(binary_string="")
  binary_string = binary_string.to_s
  unless binary_string[/\A[01]+\z/]
    raise ArgumentError.new ERROR_FORMAT % binary_string.inspect
  end
  number = 0
  binary_string.split('').reverse.each_with_index do |c, i|
    number += c.to_i * (2 ** i)
  end
  number.to_s
end

def idiomatic_convert(binary_string="")
  Integer("0b#{binary_string.to_s}")
end

def repl
  loop do
    print "\nEnter a binary string: (just press return to quit) "
    response = gets.chomp
    break if response.empty?

    print "Manual conversion:    "
    begin
      puts OUTPUT_FORMAT % [response, convert(response)]
    rescue ArgumentError => e
      puts "ERROR: #{e} (#{e.class})"
    end

    print "Idiomatic conversion: "
    begin
      puts OUTPUT_FORMAT % [response, idiomatic_convert(response)]
    rescue ArgumentError => e
      puts "ERROR: " + (ERROR_FORMAT % response.inspect)
      puts "  - Exception raised: #{e} (#{e.class}) from #{e.backtrace.first}"
    end
  end
end

puts "Welcome to the Famouse Binary to Decimal Converter!\n"
repl
puts "\nThanks for playing!"

output

$ ./bin_to_dec 
Welcome to the Famouse Binary to Decimal Converter!

Enter a binary string: (just press return to quit) 1
Manual conversion:    1 in decimal is 1
Idiomatic conversion: 1 in decimal is 1

Enter a binary string: (just press return to quit) 2
Manual conversion:    ERROR: Argument "2" must be a binary string (0 and 1 only). (ArgumentError)
Idiomatic conversion: ERROR: Argument "2" must be a binary string (0 and 1 only).
  - Exception raised: invalid value for Integer(): "0b2" (ArgumentError) from ./bin_to_dec:21:in `Integer'

Enter a binary string: (just press return to quit) "hello
Manual conversion:    ERROR: Argument "\"hello" must be a binary string (0 and 1 only). (ArgumentError)
Idiomatic conversion: ERROR: Argument "\"hello" must be a binary string (0 and 1 only).
  - Exception raised: invalid value for Integer(): "0b\"hello" (ArgumentError) from ./bin_to_dec:21:in `Integer'

Enter a binary string: (just press return to quit) 101
Manual conversion:    101 in decimal is 5
Idiomatic conversion: 101 in decimal is 5

Enter a binary string: (just press return to quit) 111
Manual conversion:    111 in decimal is 7
Idiomatic conversion: 111 in decimal is 7

Enter a binary string: (just press return to quit) 

Thanks for playing!