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Put defvisitor, defvisitors, and define forms togeher into a single mutual recursion.
In a few cases it is useful to have visitors for several types (or perhaps several different kinds of visitors) together in a mutual recursion. Here is an example showing how this can work.
;; We have sum of product terms. Each literal in the sum of products is ;; either a constant or a variable, which refers to another sum of products ;; term via a lookup table. (deftagsum literal (:constant ((value natp))) (:variable ((name symbolp)))) (defprod product ((first literal-p) (second literal-p) (third literal-p))) (defprod sum ((left product-p) (right product-p))) ;; Lookup table mapping each variable to a sum-of-products. (defalist sop-env :key-type symbolp :val-type sum-p) ;; Suppose we have a lookup table and we want to collect all the dependencies ;; of some expression -- i.e., when we get to a variable we want to collect ;; it, then look up its formula and collect its dependencies too. If the ;; table doesn't have some strict dependency order, then we might not ;; terminate, so we'll use a recursion limit. (defvisitor-template collect-deps ((x :object) (env sop-env-p) (rec-limit natp)) :returns (deps (:join (append deps1 deps) :tmp-var deps1 :initial nil) symbol-listp) ;; We'll call the function to apply to variable names ;; collect-and-recur-on-var. Note that this hasn't been defined yet -- it ;; needs to be mutually recursive with the other functions in the clique. :prod-fns ((variable (name collect-and-recur-on-var))) :fnname-template <type>-collect-deps) ;; A defvisitor-multi form binds together some defvisitor and defvisitors ;; forms into a mutual recursion with some other functions. Here, we'll just have ;; the one defvisitors form inside. (defvisitor-multi sum-collect-deps (defvisitors :template collect-deps :types (sum) ;; Normally this defvisitors form would create a visitor for a literal, ;; then product, then sum. Inside a defvisitor-multi, it instead puts ;; all of those definitions into one mutual recursion. ;; We have to do something special with the measure. Defvisitors ;; assigns an order to each of the types so that calling from one ;; visitor to another can generally reduce the measure. Therefore, we ;; only need to decrease the rec-limit when calling from a lower-level ;; type to a higher-level one -- e.g. when we reach a variable and will ;; recur on a sum. :measure (two-nats-measure rec-limit :order) ;; Since our lowest-level visitor (literal-collect-deps) is going to ;; call an intermediate function (collect-and-recur-on-var) which then ;; calls our highest-level visitor (sum-collect-deps), it's convenient ;; to set the order of the lowest-level to 1 so that ;; collect-and-recur-on-var can use 0 as the order in its measure. :order-base 1) ;; This function goes in the mutual recursion with the others. (define collect-and-recur-on-var ((x symbolp) (env sop-env-p) (rec-limit natp)) :returns (deps symbol-listp) :measure (two-nats-measure rec-limit 0) (b* ((x (mbe :logic (symbol-fix x) :exec x)) (lookup (hons-get x (sop-env-fix env))) ((unless lookup) (list x)) ((when (zp rec-limit)) (cw "Recursion limit ran out on ~x0~%" x) (list x))) (cons x (sum-collect-deps (cdr lookup) env (- rec-limit 1))))))
A
(defvisitor-multi event-name defvisitor-defvisitors-define-forms keyword-args /// post-events)
The only keyword arguments currently accepted are