+;;; This is a vaguely case-like macro that does number cross-product
+;;; dispatches. The Vars are the variables we are dispatching off of.
+;;; The Type paired with each Var is used in the error message when no
+;;; case matches. Each case specifies a Type for each var, and is
+;;; executed when that signature holds. A type may be a list
+;;; (FOREACH Each-Type*), causing that case to be repeatedly
+;;; instantiated for every Each-Type. In the body of each case, any
+;;; list of the form (DISPATCH-TYPE Var-Name) is substituted with the
+;;; type of that var in that instance of the case.
+;;;
+;;; As an alternate to a case spec, there may be a form whose CAR is a
+;;; symbol. In this case, we apply the CAR of the form to the CDR and
+;;; treat the result of the call as a list of cases. This process is
+;;; not applied recursively.