col-widther.rb

@colwidth = 100

@margin = 10

@total = 0

def spanwidth(cols)
  [(cols * @colwidth.to_i), (@margin.to_i * (cols-1))]
end

def calculate
  (1..@cols.to_i).each do | i |
    width =  spanwidth(i)
    puts "--  #{@total}  --"
    puts "--  #{@total + @margin.to_i}  --"
    puts "    [#{i}] #{width[0] + width[1]}"
    @total += (@colwidth.to_i + @margin.to_i)
  end
  puts "--  #{@margin.to_i}  --"
end

puts "Column width: "
@colwidth = gets

puts "Margin width: "
@margin = gets

puts "Total columns: "
@cols = gets

puts ". . . . . ."

if @colwidth.to_i > 1 && @margin.to_i > 1 && @cols.to_i > 1
  calculate
  puts "Total: #{@total}"
else
  puts "Oops."
end