Added a LISP version too.

src/doublesgame.lisp

@@ -0,0 +1,40 @@
+#|
+ | Copyright (C) 2017 Ortega Froysa, Nicolás <deathsbreed@themusicinnoise.net> All rights reserved.
+ | Author: Ortega Froysa, Nicolás <deathsbreed@themusicinnoise.net>
+ |
+ | This software is provided 'as-is', without any express or implied
+ | warranty. In no event will the authors be held liable for any damages
+ | arising from the use of this software.
+ |
+ | Permission is granted to anyone to use this software for any purpose,
+ | including commercial applications, and to alter it and redistribute it
+ | freely, subject to the following restrictions:
+ |
+ | 1. The origin of this software must not be misrepresented; you must not
+ |    claim that you wrote the original software. If you use this software
+ |    in a product, an acknowledgment in the product documentation would be
+ |    appreciated but is not required.
+ |
+ | 2. Altered source versions must be plainly marked as such, and must not be
+ |    misrepresented as being the original software.
+ |
+ | 3. This notice may not be removed or altered from any source
+ |    distribution.
+ |#
+
+(print "Use Ctrl+C to exit.")
+
+(let ((n 1))
+  (loop
+  	(defvar a)
+	(format t "~%2^~a=" n)
+	(setq a (read))
+	(if (= a (expt 2 n))
+	  (progn
+		(print "Correct!")
+		(incf n))
+	  (if (= a 0)
+		(progn
+		  (print "Goodbye!")
+		  (return nil))
+		(print "Wrong answer, try again.")))))