Ruby course - isbn 1

gistfile1.rb

def check_isbn13(isbn)
  total = 0
  12.times do |i|
    # puts i % 2
    if i % 2 == 0
      total += isbn[i].to_i
    else
      total += isbn[i].to_i * 3
    end
  end
  checksum = 10 - (total % 10)
  if (checksum == 10)
    checksum = 0
  end
  valid = isbn.end_with? checksum.to_s
end

def strip_isbn(isbn)
  isbn.gsub(/\-+/, "").gsub(/\s+/, "")
end

isbns = []
file = File.new("isbns", "r").each do |line|
  line = strip_isbn line
  valid = check_isbn13 line
  print "#{line} "
  puts valid ? 'valid' : 'not valid'
  isbns.push line
end

# $ ruby isbn.rb
# 9780596516178 valid
# 9781430223634 valid
# 9780321584106 valid
# 9780321743121 valid
# 9781934356470 valid
# 9780321490452 valid