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I have one single file called Exercises.rb

def ask(prompt) print prompt, ' ' $stdout.flush s = gets return s end def myreverse(s) aux="" for i in 0..s.length-1 aux=s[i] + aux end return aux end def mywordreverse(s) aux=[] s=s.split(" ") for i in 0..s.length-1 aux.unshift(s[i]) end return aux.join(" ") end def choose(s,option) case option when 1 then print myreverse(s) when 2 then print mywordreverse(s) when 3 then print "hello" else print "You gave me #{option} -- I have no idea what to do with that." end end s=ask("Write a string to reverse: ") option=ask("Choose an option. 1 - Reverse string. 2 - Reverse String words : ") choose(s,option)

I am always getting You gave MYCHOSENOPTION -- I have no idea what to do with that., no matter what option I choose. If I put an if just before the case comparing 1, it just doesn't seem to be matching the option to my strings.

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2 Answers 2

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Try this:

 case option.to_i # rest of your code...

In Ruby, 1 == "1" (or more specifically in the case of a case statement, 1 === "1") always evaluates to false. You'll need to convert one of them so that they are the same type before doing the comparison. The value that you're passing in for option is likely a String and will therefore fail for any comparisons to integers.

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Hi, thank you robbrit. That actually was my first dilemma, and I switched from 1,2,3 to "1","2","3" (actually 1,2, the 3 was just a test). to_i would solve that one problem though. What would be more efficient, convert to int, or compare the chars ?
In theory comparing the strings would be more efficient because you're not having to parse anything, however the difference is so miniscule that I doubt it would actually matter.
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FWIW, here is how I would write this program:

def ask(prompt) print "#{prompt} " gets.chomp end def myreverse(s) s.reverse end def mywordreverse(s) s.split(' ').reverse.join(' ') end def choose(s,option) case option when 1 then puts myreverse(s) when 2 then puts mywordreverse(s) when 3 then puts "hello" else puts "You gave me #{option}; I don't know what to do with that." end end $stdout.sync str = ask("Write a string to reverse: ") option = ask("Choose an option:\n1: Reverse string\n2: Reverse String words\n>") choose(str,option.to_i)

Notes:

  1. The last expression in a method is the return value; using return is almost never needed or desirable in Ruby.
  2. There exist built-in methods for reversing strings and arrays. (I understand if you are doing this for an exercise.)

  3. It is cumbersome to iterate arrays or strings in Ruby using for. Instead, you should use

    my_str.each_char do |char| # use the single-character string `char` here end my_array.each do |item| # use the item here end

  4. You can use $stdout.sync to force output to always be flushed.

  5. You need to use chomp on your string to remove the trailing newline always included when the user presses Enter.
  6. As pointed out by @robbrit, the core of your problem is that the return value of gets is a String, and you are comparing it to a Fixnum. I've used to_i in my code above to convert the string to an integer for comparison.
  7. I've used puts instead of print for the output so that I get a newline at the end and do not leave the user with their next command prompt on the same line as the output.
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Hi Phrogz, I actually thought i knew my answer, but i am so fond of yours, that i will stick with it. My first problem was that comparison 1 === "1" is actually false. My second problem was that chomp, which was missing, and that one took me a hard time. I actually got there by checking the length of my option string. As for point 2, and 3, you have a keen eye :-). I created these ones to support an interview process, abstract to the language, so i answered it the most low-level/nearer to C way. In each language (and i like ruby more and more btw ) there will be different ways to solve this.
Anyhow, i have learned from your answer and thank you for it. Cheers.

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