1. Function "foo" [Var "x",Var "y"] (BinOp Plus (Var "x") (Call "foo" [Var "y",Float 4.0]))
    2. ready> def foo(x y) x+y; y;
    3. Function "foo" [Var "x",Var "y"] (BinOp Plus (Var "x") (Var "y"))
    4. ready> def foo(x y) x+y );
    5. "<stdin>" (line 1, column 18):
    6. unexpected ")"
    7. ready> extern sin(a);
    8. Extern "sin" [Var "a"]
    9. Goodbye.