Arc Forum | ((a 'b) (c 'd)) (('a b) ('c d)) I just noticed none of your alist examples ...

Arc Forum

2 points by fallintothis 5135 days ago | link | parent

  ((a 'b) (c 'd))
  (('a b) ('c d))

I just noticed none of your alist examples work with the atoms-imply-lists thing -- unless you ditch list-indexing, like (xs 0). That is, even if a, b, c, and d are all atoms,

  ((a b) (c d))

would not be an explicit alist, since

  (a b) == (list a b)

and

  (c d) == (list c d)

Thus,

  ((a b) (c d)) == ((list a b) (list c d))

which throws an error since (list c d) isn't a proper index (i.e., isn't a number).

Even if you could write alists that way, you'd be restricted to only those with atom cars. Personally, I can't think of the last time I needed a literal alist. If I wanted to write them that much, couldn't use quote, and couldn't bare to use list, I'd probably just do

  (def assoc-list args (pair args))

  arc> (assoc-list 'a 1 'b 2)
  ((a 1) (b 2))

and do away with complicating evaluation rules in such fragile ways.