Have you seen destructuring of rest args in the current master branch?
(defn foo [& {:keys [a b c]}] [a b c])
(foo :a 1 :c 3)
=> [1 nil 3]
With this last bit of sugar in place I am extremely happy with
Clojure's arg handling.
Please don't misunderstand this post - it is not asking for a change
of syntax, just trying to understand something.
Clojure has chosen positional parameters (just like for Lisp, C, C++,
Java, Ruby, Python, Prolog, ...)
Smalltalk composes a full method name from a prefix-name + named
parameters.
[obj] prefix key1: x key2: y key3: z
The [obj] part above is an artifact of the single-dispatch model, and
is irrelevant to this discussion, so I'll leave it out from here on.
Importantly, the method name here is a composite:
#prefix:key1:key2:key3
This leads to remarkably readable function calls:
1. (schedule project: p1 after: p2 before: p3 priority: 7)
;; calls schedule:project:after:before:priority
vs.
2. (schedule p1 p2 p3 7)
Note that 1. in no way requires arbitrary ordering of keywords, maps,
de-structuring, etc. The positions are still fixed, just keyword-
prefixed. It's like taking the Clojure parameter list
(defn schedule
[project before after priority] ....)
and requiring those parameter names (or a formal version thereof which
is meant to be part of the interface) at the calling sites.
An only-slightly-strained analogy would be only allowing %1 %2 for
formal parameters in all function bodies
(defn schedule [%1 %2 %3]
(.... stuff with %1 %2 ...))
or
(deftype Person [name age])
and then requiring
(1 joe) instead of (:name joe)
Just curious
- what folks think of fixed-positional-keyword params
- whether it was considered for Clojure
Thanks!
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