Re: [PATCH] Clojure-like syntactic sugar for an anonymous function literal

[Tassilo Horn <tsdh@gnu.org>]

Oleh <ohwoeowho@gmail.com> writes:

>>  > The most popular library in MELPA, https://github.com/magnars/dash.el,
>>  > implements it (for a long time) like this:
>>  >
>>  >     (--map (* it it) '(1 2 3))
>>  >     ;; => (1 4 9)
>>  >
>>  > With my approach, it's:
>>  >
>>  >     (mapcar #(* % %) '(1 2 3))
>>  >     ;; => (1 4 9)
>>
>> That looks almost like Perl!  Now I'm -2.  Just require dash.
>
> How is `dash' better? `--map' is a macro:
>
>     (defmacro --map (form list)
>       "Anaphoric form of `-map'."
>       (declare (debug (form form)))
>       `(mapcar (lambda (it) ,form) ,list))
>
> `dash' also gives other ~40 macros that look like this, littered all
> over the code in the MELPA, so it's impossible to go on without
> understanding what `dash' does.

FWIW, I favor your Clojure-like syntax over anaphoric macros.  And one
benefit is that you're not restricted to one list to map over as in
--map.  E.g., your approach works out of the box with

  (cl-mapcar #(- %5 %4 %3 %2 %1) list1 list2 list3 list4 list5)

for which there is no dash equivalent.  Of course, --map could be
extended to create args (it1 ... itN) if more than one list is given.

BTW, do you also support %& to declare that the lambda has a &rest arg
so that you can do

  (apply #'cl-mapcar #(apply #'- (reverse %&)) list-of-lists)

?

So basically I like that syntax (or maybe #l(...) or #fn(...)) and would
consider using it where it makes sense.  But as others already
mentioned, those places are much fewer than in an almost purely
functional language like Clojure.

Bye,
Tassilo