stack = Array.new

while true
	printf "Enter next value/command: "
	str = gets.chomp!
begin
	if str == "+"
		if stack.length < 2 
			raise "Not enough on stack!"
		end
		op1 = stack.pop
		op2 = stack.pop
		stack.push(op1 + op2)
	elsif str == "-"
		if stack.length < 2 
			raise "Not enough on stack!"
		end
		op1 = stack.pop
		op2 = stack.pop
		stack.push(op1 - op2)
	elsif str == "*"
		if stack.length < 2 
			raise "Not enough on stack!"
		end
		op1 = stack.pop
		op2 = stack.pop
		stack.push(op1 * op2)
	elsif str == "/"
		if stack.length < 2 
			raise "Not enough on stack!"
		end
		op1 = stack.pop
		op2 = stack.pop
		stack.push(op1 / op2)
	elsif str == "^"
		if stack.length < 2 
			raise "Not enough on stack!"
		end
		op1 = stack.pop
		op2 = stack.pop
		stack.push(pow (op1, op2))
	elsif str == "i"
		printf "There is a total of %d items on the stack.\n", stack.length
		print "[" 
		stack.each {|x| print x, ", " }
		print "]\n"
	elsif str[0,1] == "p"
		stack.pop
	elsif str[0,1] == "q"
		exit
	else 
		stack.push(Float(str))
	end
rescue RuntimeError => error
	puts error
rescue ArgumentError
	puts "You entered an invalid command. Ignoring."
end
end