proc.rb

def gen_log_base(base)
  return Proc.new { |num| Math.log(num, base) }                                                                                                                    
end

log2 = gen_log_base(2)
log10 = gen_log_base(10)

puts log2.call(4)
puts log10.call(100)

=begin
Output:
2.0
2.0
=end