Ruby program that asks the user for a number num and computes either the sum or the product of all numbers starting at 1 until this number.

sum_or_product.rb

def sum_or_product
    print 'Enter any number bigger 1: '
    num = gets.to_i
    
    print 'sum [s] or product [p]? '
    opt = gets.chomp
    
    if opt == 's'
        (1..num).inject :+
    elsif opt == 'p'
        (1..num).inject :*
    else
        p "There is no option like '#{opt}', start again.."
    end
end