Here is the "father of all dispatchers". It returns a function that depends on a tag, and compares this tag against the three major design axes of pico:

All the other grammar entities (such as NBR, TAB,...) 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: