;; Let's call this language Tull (makes it easy to refer to)
;; This language is an expansion of the lambda calculus with 
;; 1. if expressions
;; 2. lambda expressions with 0 or more parameters
;; 3. procedure applications with 0 or more parameters
;; 4. Numbers!

;; This is the concrete syntax for Tull

 <exp>    ::==  
	  |  <number>
	  |  <varref>
	  |  (lambda (<var>*) <exp>)
	  |  (<exp>+)
	  |  (if <exp> <exp> <exp>)