Introduction To Ruby
For in

The while and until statements were all examples of condition-controlled loops. For/in loops allow you to create loops which are controlled by count. This can be a more natural way to write code when the purpose of the loop is to count and repeat a specific number of times.

Example 1

This example refactors the ones we used for while and until into a for/in loop. We use a range object to specify the start and end of the counting. We also use a stepper or counter variable.

# for/in

for x in 1..10 do
  puts x


Example 2

We can use the step method with our range object to specify how we want to do the counting.

# for/in stepped

for x in (10..100).step(10) do
  puts x


Example 3

You can create range objects using floats too. Check out the following example,

# for/in stepped with floats

for x in (0.0..1.0).step(0.1) do
  puts x


This is an interesting example. It gives you indication of the precision issues that you can get with floating point numbers,

Output from Ruby script

Example 4

You can create range objects for your loop using variables. This program allows the user to specify the start and end of the loop.

# for/in 4

print "Enter the start value for the loop: "
start = gets.chomp.to_i

print "Enter the end value for the loop: "
finish = gets.chomp.to_i

for i in start..finish do
  puts i



  1. Write a program that allows a user to enter a message and the number of times that they want to repeat that message.
  2. Write a program to output the 8 times table.
  3. Write a program that lists the numbers 1 to 20 along with their squares, cubes and square roots.
  4. Write a program that allows the user to input 10 scores. At the end of the program, output the total, mean average, highest and lowest numbers. Remember to set the total to 0 before the loop. You will also need to establish values for your minimum and maximum variables before the loop.
  5. Write a program that outputs 6 random lottery numbers for the national lottery.
  6. Adapt the last program so that it outputs 3 sets of 6 lottery numbers. To do this, you will need to nest a loop inside a loop. Take care with your indentation so that it is clear which code belongs to which loop.