> On May 7, 2019, at 1:29 PM, zeRusski <vladilen.ko...@gmail.com> wrote:
>
> It just names the threaded value. Did I overlook anything?
>
> That's right, nothing fancy. Think let-binding the threaded value at that
> point. #:with id ~ would achieve the same thing, so as it is now #:as is
> redundant. With #:do both #:with and #:as are redundant, really.
>
> Let me point out that if ~> specified an identifier (as suggested in my first
> response) you could co-mingle two threaded computations, keeping separate
> concerns that don’t matter as opposed to bundling them up in structs or lists
> or whatever you have to do if you have only one. At first I thought #:as
> would you let you do so, but that’s not correct.
>
> Ok, this one I don't quite understand. My first thought went as far as to
> weave multiple computations where each #:as would capture continuations and
> macro would keep these "threads" separate, but now I'm thinking you mean this:
>
> (~> 1 #:as ~a
> ;; now ~a is being threaded
> (add1 ~a) ;=> 2
> 2 #:as ~b
> ;; now ~b is being threaded
> (add1 ~b) ;=> 3
> ;; simply use whatever ~a was last
> (+ ~a ~b) ;=> 5
> #:as ~a
> ;; continue to thread ~a
> (add1 ~a) ;=> 3
> (list ~a ~b))
> ;; => (list 3 5)
Think:
(~> (x 0)
(add1 x)
(sin
(~> (y 1)
(sub1 y]
(+ x y)))
(* pi x))
This looks equally simple and is equally easy to read. If you wish to emphasize
the “hole variable” make sure its name has a certain shape, say ~x.
But now the threading has precise syntactic boundaries, and the implementation
gets away without any assignments (which I assume #:as uses).
— Matthias
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