Ruby's times method and for loop does the same thing, but what are the respective processes?

Question

I have a paradigm where the purpose is to calculate "the total accumulated from 'variable from' to 'variable to'". I got two methods, but I don't know exactly what steps they go through.

The first is the times method. I don't understand what (to - from +1) produces and why (i + from)? Also, this code throws syntax error, unexpected end, expecting end-of-input, I don't know where I am going wrong .

from = 10
to = 20
sum = 0
  (to - from +1).times to |i|
    sum = sum + (i + from)
  end
puts sum

Then there is the for loop. I can't understand what is the "total sum accumulated from 'variable from' to 'variable to'", what is the process of adding it?

from = 10
to = 20
sum = 0
for i in from..to
  sum = sum + i
end
puts sum

I'm bad at math, thank you all.

Answer 1

Here are a few idiomatic ways of solving this problem in Ruby. They might be a little easier to follow than the solution you proposed.

sum = 0

10.upto(20) do |i|
  sum = sum + i
end

For the first iteration of loop, i will = 10, the second, i will = 11 and so "up to" 20. Each time it will add the value of i to sum. When it completes, sum will have a value of 165.

Another way is this:

10.upto(20).sum

The reason this works is that 10.upto(20) returns an Enumerator. You can call sum on an Enumerator.