Using Forth in a Concept-Oriented Computer Language Course

We describe a way of teaching fundamentals of Language Systems (for second-year Computing students), without having to compromise the use of a simple grammar owing to hardware limitations which need no longer apply in this setting.We adopt a top-down approach, reading from right-to-left and splitting the input string on the rightmost operator appropriate to that level. The target platform is Reversible Virtual Machine (RVM) Forth, so a postfix translation is the aim. We introduce a basic arithmetic grammar and expand it during the course to allow unary minus, floating point and function application; this shows how type information can be generated in one pass and resolved in a second, via an internal intermediate code. Each version of the grammar has its productions mapped onto a system of equations which serve as the specification for the implementation functions.