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4 points by nex3 5888 days ago | link | parent

The more I think about these scanners, the cooler they seem. It's a very neat abstraction, and a great way to integrate laziness into Lisp in a very Lisp-y manner.

1 point by almkglor 5888 days ago | link

It would be neat too if function application would destructure using Arc-side 'car and 'cdr (Scheme side '_car '_cdr, or '__car '__cdr on Arc-wiki now that we have FFI). Basically the requirement for 'apply would be a scanner, not a 'cons; after all, 'apply does not mutate the applied list.

However as is it's possible to use p-m: or kennytilton's dsb (which should really be ds-b: and put on the arc-wiki.git) for destructuring scanners.

Also the syntax for creating scanners should really be neater. Possibly this might help:

  (mac scanner args
    (let (a d) nil
      ( (afn ((opt val . args))
            (iso opt ''car)
              (= a val)
            (iso opt ''cdr)
              (= d val)
              (err:tostring:pr "Unknown option - " opt))
          (if args (self args)))
      (w/uniq (a-v d-v a-valid d-valid)
        `(let (,a-v ,d-v ,a-valid ,d-valid) nil
             'car (fn ()
                    (if ,a-valid ,a-v
                                 (= ,a-valid t
                                    ,a-v ,a)))
             'cdr (fn ()
                    (if ,d-valid ,d-v
                                 (= ,d-valid t
                                    ,d-v ,d)))))))) 
'inf-iter can then be defined somewhat more neatly as:

  (def inf-iter (f c)
      'car c
      'cdr (inf-iter f (f c))))

All the above untested of course, including the grandparent post ^^ I'm sitting bored in the office ^^


4 points by nex3 5888 days ago | link

Yeah, agreed. In general, I'd like to see ac.scm calling out to Arc functions as much as possible, to maximize the power of in-Arc tinkering via redef/defm, like scanner.