# revised_gpa: version of gpa.rb that allows use as a library
#   In particular, this version can be run from the command
#   prompt by typing
#       ruby revised-gpa.rb
#   or can be loaded into another file to provide the
#   convert_to_numbers function as a utility to be used
#   in a larger project

# string(ascii) -> array(float)
# precondition: text is not empty
def convert_to_numbers(text)
  letters = text.split(' ')
  numeric_values = letters.map do |c|
    if c == 'A' || c == 'a'
      4.0
    elsif c == 'B' || c == 'b'
      3.0
    elsif c == 'C' || c == 'c'
      2.0
    elsif c == 'D' || c == 'd'
      1.0
    else
      0.0 # treat all others as F
    end
  end
end

def main
  puts "Enter grades (as A, B, C, etc.), entering a blank line to stop:"
  total = 0.0
  count = 0
  while ( (line = gets) && !line.chomp.empty? )
    nums = convert_to_numbers line
    nums.each { |x| total += x }
    count += nums.length
  end

  if count == 0
    puts "You must take classes to have a semester GPA!"
  end
  puts "Semester GPA: #{total / count}"
end

if __FILE__ == $0

  main

end