<pre>
$ ./a.out
ready> def foo(x y) x+foo(y, 4.0);
-ready> Parsed an function definition.
+ready> Parsed a function definition.
ready> def foo(x y) x+y y;
-ready> Parsed an function definition.
+ready> Parsed a function definition.
ready> Parsed a top-level expr
ready> def foo(x y) x+y );
-ready> Parsed an function definition.
+ready> Parsed a function definition.
ready> Error: unknown token when expecting an expression
ready> extern sin(a);
ready> Parsed an extern