Ruby sentinel loop not working as expected (Seven Languages In Seven Weeks)

Question

Just started working through the Ruby chapter in Mr. Tate's "Seven Language in Seven Weeks".

For the bonus question in Day 1, I am to generate a "random" number, read a user's guess from the input, and compare the guess to my "random" number, then prompt the user to continue guessing with the begin loop. However, the loop seems to terminate regardless of what the value of the string the user inputs.

# file : day1_bonus.rb
# Seven Languages In Seven Weeks
#
# Guess a random number!

again = "y"

begin
  print "Enter a number between 0 and 9: "
  number = gets.to_i
  randNum = rand(10)

  if number == randNum
    puts 'You guessed correctly!'
  else
    puts 'You guessed incorrectly.'
  end

  print "Play again? (y/n): "
  again = gets
  again.chomp   # remove carriage return
end while again == "y"

Output:

Enter a number between 0 and 9: 3
You guessed incorrectly.
Play again? (y/n): y
nil

Fair enough question, but here's some tips on how to do debugging in Ruby http://stackoverflow.com/q/3955688/38765 — Andrew Grimm, Mar 30 '12 at 03:55
@AndrewGrimm: Thank you, I was wondering how I might go about debugging in the REPL. I will take a look at this. — dtg, Mar 30 '12 at 04:02

score 4 · Accepted Answer · answered Mar 30 '12 at 02:04

4

There are two versions of chomp. The regular chomp and bang chomp!. The difference being: regular returns modified string (and leaves source alone) while the bang version modifies original string in-place.

So, in your code you chomp the carriage return and throw away this work. Either do this

again = again.chomp

or this

again.chomp!

answered Mar 30 '12 at 02:04

Sergio Tulentsev

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Thank you very much! Also, I noticed that I need to convert the value of number using `to_i` method. Otherwise it won't work. I will correct it above. – dtg Mar 30 '12 at 03:42

Ruby sentinel loop not working as expected (Seven Languages In Seven Weeks)

1 Answers1