The 'upto' method in Ruby

Question

I'm learning Ruby, and there has been a bit of talk about the upto method in the book from which I am learning. I'm confused. What exactly does it do?

Example:

grades = [88,99,73,56,87,64]
sum = 0
0.upto(grades.length - 1) do |loop_index|
    sum += grades[loop_index]
end
average = sum/grades.length
puts average

Answer 1

My example would have been this:

1.upto(5)  { |i| puts "Countup: #{i}" }

So what you're actually doing here is saying, I want to count up from 1 to the number 5, that's specifically what this part is saying:

1.upto(5)

The latter part of code (a block) is just outputting the iteration of going through the count from 1 up to 5. This is the output you might expect to see:

    Countup: 1
    Countup: 2
    Countup: 3
    Countup: 4
    Countup: 5

Note: This can be written is another way if you're using multilines:

1.upto(5) do |i|
puts "Countup: #{i}"
end

Hope this helps.

Answer 2

From http://www.ruby-doc.org/docs/ProgrammingRuby/html/ref_c_integer.html#upto:

upto int.upto( anInteger ) {| i | block }

Iterates block, passing in integer values from int up to and including anInteger.

5.upto(10) { |i| print i, " " }

produces:

5 6 7 8 9 10