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3 points by kennytilton 4708 days ago | link | parent

The syntax to add rest args, if it followed the CL example, would be:

  (dsb (r1 &o o1 &r rest &k k1) data ....)
If data was (1 2 'k1 3) then most params would be bound as expected and then rest would be bound to (k1 3).

But now the data (1 2 'k1 3 4) causes an error "Key list is not even", ie, once you say &k you undertake certain obligations as the caller. Even if you even up the list:

   (1 2 'k1 2 3 5) get an error "3 is an invalid keyword", because 3 appears in a keyword position. This can be avoided by announcing your intention to have undeclared keywords:

   (a b &rest rest &key k1 &allow-other-keys)
That of course is CL, and it kinda makes my day that if I were crazy enough to extend dsb in Arc I would end up with:

   (a b &r rest &k k1 &aok)

1 point by kennytilton 4707 days ago | link

"...if I were crazy enough to extend dsb..."

Was there ever any doubt? :)

Still requiring extensions from earlier posts:

  (def dsb-params-parse (params)
    (withs (reqs nil key? nil opt? nil keys nil opts nil
          rest (mem '&r params)
          rest-var (cadr rest)
          aok? (find '&aok
           resting? nil
           no-mas nil)
    (each p params
      (if no-mas (assert nil "No params &aok, OK?" ',params)
        (is p '&o) (do (assert ~opt? "Duplicate &o:" ',params)
                       (assert ~key? "&k cannot precede &o:" ',params)
                     (= opt? t))
        (is p '&k) (do (assert ~key? "Duplicate &k:" ',params)
                       (= key? t))
        (is p '&r) (= resting? t)
        (is p '&aok) (= no-mas t)
        key? (push-end p keys)
        (and opt? (no resting?)) (push-end p opts)
        (no resting?) (do (assert (~acons p) "Reqd parameters need not be defaulted:" p)
                           (push-end p reqs))))
    (prt 're-obj!!!!! reqs opts rest-var keys aok?)
    (obj reqs reqs opts opts rst rest-var keys keys aok? aok?)))
And man was I happy to have the above as a breakout from the macro itself:

  (mac dsb (params data . body)
  (w/uniq (tree kvs valid-keys aok?)
    `(withs (,tree ,data
              ,@(let plist (dsb-params-parse params)
                  (prn `(reqs ,plist!reqs))
                  (prn `(rst ,plist!rst))
                  (prn `(keys ,plist!keys))
                  (prn `(&aok ,plist!aok?))
                  (with (n -1)
                    (+ (mappend [list _ `(nth ,(++ n) ,tree)] plist!reqs)
                      (mappend [list (carif _) `(if (< ,(++ n) (len ,tree))
                                                    (nth ,n ,tree)
                                                  ,(cadrif _))] plist!opts)
                      `(,plist!rst (nthcdr ,(++ n) ,tree))
                      `(,valid-keys ',plist!keys)
                      `(,aok? ',plist!aok?)
                      `(,kvs (do (prt 'foing ,valid-keys)
                                 (when (and ,plist!rst ,valid-keys)
                                   (assert (even (len ,plist!rst)) "Keyword list not even" ,plist!rst)
                                   (let ,kvs (pair ,plist!rst)
                                     (prt 'vetting ,valid-keys 'againt ,kvs)
                                     (unless ,aok?
                                       (assert (all [find (car _) ,valid-keys] ,kvs)
                                         "Invalid key in" (map car ,kvs)))
                                     (prt 'kvs!!!!! ,kvs)
                      (mappend [list (carif _)
                                 `(do (prt 'kvs!!! ',(carif _) ,kvs)
                                      (aif (assoc ',(carif _) ,kvs)
                                        ,(cadrif _)))] plist!keys)))))
What is missing (largely) is graceful handling of invalid use.


1 point by almkglor 4707 days ago | link

> What is missing (largely) is graceful handling of invalid use.

(err:tostring:write ...) works fine for me for reporting errors and aborting