add first example

infiniteArithmetic.fr

@@ -0,0 +1,17 @@
+data Expr
+  = Val Int
+  | Add Expr Expr
+  | Mul Expr Expr
+
+eval :: Expr -> Int
+eval (Val n)   = n
+eval (Add a b) = eval a + eval b
+eval (Mul a b) = eval a * eval b
+
+exprs :: [Expr]
+exprs = map Val [0..] ++
+        [ Add a b | a <- exprs, b <- exprs ] ++
+        [ Mul a b | a <- exprs, b <- exprs ]
+
+main :: IO ()
+main = print (take 10 (map eval exprs))