Loops are used to execute the same block of code a specific number of times. If we want to output “I love Ruby!” message certain times, we can use loops and set a counter to count how many times it is looping over.
My question was “should I write a counter before or after puts message? “
Well.. it depends or doesn’t matter.
But it made me confused.
At the end of challenge, I found both ways worked so I kept going. But now it is time to figure out how it works and what is the difference. So I won’t be frustrated next time.
Let’s see simple while loops below.
We set a counter (valuable i) equal to 0 and increment by 1. If i hits 5, it executes.
Case 1. Increment `i` after `puts`
i = 0
while i < 5
puts i
i += 1
end
result --> 0,1,2,3,4
First result is 0. i is still equal to 0 because we wrote i += 1 after puts i.
1 is added at the next line. And it continues.
When i = 4, it outputs 4. Right after puts line, i becomes equal to 5 and the loop ends. At the next round, i is not less than 5 anymore so it executes without outputting 5.
Case 2. Increment `j` before `puts`
j = 0
while j < 5
j += 1
puts j
end
result --> 1,2,3,4,5
First output is 1, not 0. j is incremented just before puts message.
When j = 4, it increments by 1, outputs 5 and executes.
Return value changes by writing counter before or after puts.
In the case 2, I thought it would not output 5 . Because it is supposed to be less than 5!? I was confused when it outputs 5 . But that’s right, if I look the code carefully, it makes sense. It does not mean greater than 5 but simply puts is wrote after the counter is incremented.
By the way, if we don’t output counter, we may not realize the difference.
Let’s say we want to output message I love Ruby! in both case1 and case 2. Both outputs message 5 times and we have the same results like:
result -->
I love Ruby!
I love Ruby!
I love Ruby!
I love Ruby!
I love Ruby!
Both ways work the same. I was unconsciously doing that so I found the difference between case 1 and case 2, aha moment came to me!
In the following codes, I only changed arithmetical operator from less than (<) to less than or equal to (<=).
Case 3. Increment `i` after `puts` (same as case 1, but `i <= 5`)
i = 0
while i <= 5
puts i
i += 1
end
result --> 0,1,2,3,4,5
Case 4. Increment `j` before `puts` (same as case 2, but `j <= 5`)
j = 0
while j <= 5
j += 1
puts j
end
result --> 1,2,3,4,5,6
I had another belief that it only outputs 5 times either we use < 5 or <=5. But if we understand case 1 and case 2, we know that is not true.
It was fun to test codes.
When I finally understand the difference, it makes me happy :)