examples/ruby/number_guessing.rb

hidden = rand(200)
# puts hidden

print "Type in your guess: "
guess = gets.to_i

if guess == hidden
    puts "Hit"
elsif guess < hidden
    puts "Your guess is smaller that the hidden number"
else
    puts "Your guess is bigger that the hidden number"
end

We use the rand function to generate a random number. If we called it without any parameter, rand would return a floating point number between 0 and 1. As we passed a whole number to it, the rand function generated a whole number between 0 and 200, the number we gave.

There is a commented out line printing the hidden value back. I used it to be able to test the code which was comparing my input to the hidden number.

Then we use the print function to ask the user to type in a number. We use the print functions instead of the puts function to avoid adding a trailing newline. So the cursor will appear on the same line where the request was printed.

gets reads in whatever we type in response. to_i converts it to integer. (By default when we read in something from the standard input, that will be a string. Even if it only contains numbers. We have to tell Ruby to convert it to an integer.)

Then we have 3 cases depending the relative values of the hidden and guess variables.