All the other grammar entities (such as
are to be considered as literals: their evaluation is trivial ("a number evaluates
to a number"). So the
else clause of the dispatcher contains the
eval_identity. Needless to say, this function does nothing.
It calls the appropriate function to evaluate that particular kind of syntax.
Important Remark: To understand the how-and-why of all these dispatchers that call each other, notice that the structure of the interpreter completely follows the basic design space of Pico: