Arc Forum | Yes, that's what I'm saying. I understand now that sometimes it is useful to pul...

Arc Forum

1 point by Pauan 5158 days ago | link | parent

Yes, that's what I'm saying. I understand now that sometimes it is useful to pull in a variable from an outer scope, but sometimes you want the behavior of letrec. I'm pretty sure letrec would be trivial to write as a macro, so this discussion is more about which should be the default. Do people usually want the outer scope, or the inner?

P.S. I whipped up a quick version of letr; it seems to work okay:

  (mac letr (var val . body)
    `(let ,var nil
       (assign ,var ,val)
       ,@body))

P.P.S. Adding more syntax would also solve it, but I actually would prefer to give them two different names. It just seems cleaner and less cluttered to me.

2 points by akkartik 5158 days ago | link

That makes sense. But why is:

  (letr rec (fn (x) (rec x))
    (rec 3))

superior to

  (let rec (afn (x) (self x))
    (rec 3))

?

-----

1 point by Pauan 5158 days ago | link

For me, two reasons:

1) afn is somewhat of an anomaly. When I see "fn" I know "this is a function" but when I see "afn" I have to pause for a split second to realize what it does.

2) Pattern recognition due to redundancy. When I glance at the first version, my eyes quickly notice that there are 3 references to "rec", and thus I immediately form a pattern in my mind. But in the second version, there are two references to the same function: self and rec. This adds an additional cognitive overhead for me.

In other words, the first one appears less cluttered to me because it has fewer unique elements, and because "fn" is more familiar to me than "afn".

It's not a huge deal, but I would like to reduce the cognitive overhead of reading and writing code as much as I can, which is one of the things I really like about Arc: it's clean, simple, and short, but allow tons of flexibility to change the language to suit the way you think.

-----