Basic user interaction

atom.py

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+class Atom:
+	pass

lisp.py

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+import atom
+
+class Lisp:
+	def evaluate(self, expression: str):
+		return expression.upper()

repl.py

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+import lisp
+
+def main():
+	print("Welcome message.")
+	state = lisp.Lisp()
+	# REPL Loop
+	while True:
+		expression: str = input("> ")
+		print(state.evaluate(expression))
+
+if __name__ == "__main__":
+	main()