I agree; the nested case is a bit difficult for humans to parse.
I wonder if there's a way to make (fn (x) ...) even more lightweight.
What if, to do the same thing, we had a new anonymous function syntax?
{x ...}
It would work somewhat like this:
arc> (let my-fn {arg (string "I got " arg)}
(my-fn "this thing"))
"I got this thing"
This is somewhat analogous to "let"
(let x ...)
It could also allow for multiple arguments, like this:
{(x y} ...)
Allowing for multiple arguments prevents destructuring-bind style function calls, though, which is a downside. I guess you could use other kinds of brackets for that?
{{x y} ...};; this would be non-destructuring-bind
{(x y) ...};; this is destructuring-bind
{{(x y} ...);;; this is the same as #2; it would destructuring-bind the first argument, a list.
Heck, we could even build it into the existing anonymous function syntax:
As per akkartik's comment, we already have multi-argument anonymous functions in anarki:
([prn _1 _2] "hello " "there")
But yeah maybe having full lambda list capabilities in the anonymous function would be cool.
([((a b) c) (prn c b a)] (list "is" "name ") "my ")
So if the first argument to the bracket function is a list, it acts as a lambda list.
But this interferes with the arc special syntax of having lists act as functions on their indices. Because the following is already valid arc code:
(let x (list 1 2 3)
(x 2))
;; > 3
In that case having different delimiters might be the way to go. So your brace notation would be used for anonymous functions with full lambda list capability.
(let x (list 1 2)
({((a b) c) (prn c b a)} x 3))
Edit: trying some other formatting...
(with (f {((a b) c)
(prn c b a)}
x (list 1 2))
(f x 3))
I was thinking that if you have an even simpler way to bind specific variables in the function call, you can nest these anonymous functions, and not have the arguments shadow each other.
> In that case having different delimiters might be the way to go. So your brace notation would be used for anonymous functions with full lambda list capability.
Yeah, I think you're right. The square-brace anonymous function could have optionally a curly-braced first argument. If that argument isn't there, it works as the square-braced anonymous function currently does. If that argument is there, it's the arguments to that function. Since curly braces aren't used anywhere else in Arc, it can only be parsed in that one way.
But perhaps this is all a lot of work to avoid writing `fn (arg1 arg2)`. Other than golfing, I don't know if you really want to nest functions this way. And this seems like a waste of the only paired characters Arc doesn't use.
"And this seems like a waste of the only paired characters Arc doesn't use."
I don't think even the [] syntax really pulls its weight. Between (foo [bar baz _]) and (foo:fn_:bar baz _), the latter is already more convenient in some ways, and one advantage is that we can define variations of (fn_ ...) under different names without feeling like these variations are second-class.
(Arc calls it "make-br-fn" rather than "fn_", but I wanted the example to look good. :-p )
Personally, I've never gotten comfortable with the colon intrasymbol syntax. Even in your example, I'm having trouble parsing it right now. I really don't like how it makes "bar" look like part of the first part, not the second.
