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diff --git a/src/content/tils/2021/04/24/clojure-autocurry.adoc b/src/content/tils/2021/04/24/clojure-autocurry.adoc deleted file mode 100644 index a2c2835..0000000 --- a/src/content/tils/2021/04/24/clojure-autocurry.adoc +++ /dev/null @@ -1,135 +0,0 @@ -= Clojure auto curry -:sort: 1 -:updatedat: 2021-04-27 - -:defcurry-orig: https://lorettahe.github.io/clojure/2016/09/22/clojure-auto-curry - -Here's a simple macro defined by {defcurry-orig}[Loretta He] to create Clojure -functions that are curried on all arguments, relying on Clojure's multi-arity -support: - -[source,clojure] ----- -(defmacro defcurry - [name args & body] - (let [partials (map (fn [n] - `(~(subvec args 0 n) (partial ~name ~@(take n args)))) - (range 1 (count args)))] - `(defn ~name - (~args ~@body) - ~@partials))) ----- - -A naive `add` definition, alongside its usage and macroexpansion: - -[source,clojure] ----- -user=> (defcurry add - [a b c d e] - (+ 1 2 3 4 5)) -#'user/add - -user=> (add 1) -#object[clojure.core$partial$fn__5857 0x2c708440 "clojure.core$partial$fn__5857@2c708440"] - -user=> (add 1 2 3 4) -#object[clojure.core$partial$fn__5863 0xf4c0e4e "clojure.core$partial$fn__5863@f4c0e4e"] - -user=> ((add 1) 2 3 4 5) -15 - -user=> (((add 1) 2 3) 4 5) -15 - -user=> (use 'clojure.pprint) -nil - -user=> (pprint - (macroexpand - '(defcurry add - [a b c d e] - (+ 1 2 3 4 5)))) -(def - add - (clojure.core/fn - ([a b c d e] (+ 1 2 3 4 5)) - ([a] (clojure.core/partial add a)) - ([a b] (clojure.core/partial add a b)) - ([a b c] (clojure.core/partial add a b c)) - ([a b c d] (clojure.core/partial add a b c d)))) -nil ----- - -This simplistic `defcurry` definition doesn't support optional parameters, -multi-arity, `&` rest arguments, docstrings, etc., but it could certainly evolve -to do so. - -I like how `defcurry` is so short, and abdicates the responsability of doing the -multi-arity logic to Clojure's built-in multi-arity support. Simple and -elegant. - -Same Clojure as before, now with auto-currying via macros. - -== Comparison with Common Lisp - -My attempt at writing an equivalent for Common Lisp gives me: - -[source,lisp] ----- -(defun partial (fn &rest args) - (lambda (&rest args2) - (apply fn (append args args2)))) - -(defun curry-n (n func) - (cond ((< n 0) (error "Too many arguments")) - ((zerop n) (funcall func)) - (t (lambda (&rest rest) - (curry-n (- n (length rest)) - (apply #'partial func rest)))))) - -(defmacro defcurry (name args &body body) - `(defun ,name (&rest rest) - (let ((func (lambda ,args ,@body))) - (curry-n (- ,(length args) (length rest)) - (apply #'partial func rest))))) ----- - -Without built-in multi-arity support, we have to do more work, like tracking the -number of arguments consumed so far. We also have to write `#'partial` -ourselves. That is, without dependending on any library, sticking to ANSI -Common Lisp. - -The usage is pretty similar: - -[source,lisp] ----- -* (defcurry add (a b c d e) - (+ a b c d e)) -ADD - -* (add 1) -#<FUNCTION (LAMBDA (&REST REST) :IN CURRY-N) {100216419B}> - -* (funcall (add 1) 2 3 4) -#<FUNCTION (LAMBDA (&REST REST) :IN CURRY-N) {100216537B}> - -* (funcall (add 1) 2 3 4 5) -15 - -* (funcall (funcall (add 1) 2 3) 4 5) -15 - -* (macroexpand-1 - '(defcurry add (a b c d e) - (+ a b c d e))) -(DEFUN ADD (&REST REST) - (LET ((FUNC (LAMBDA (A B C D E) (+ A B C D E)))) - (CURRY-N (- 5 (LENGTH REST)) (APPLY #'PARTIAL FUNC REST)))) -T ----- - -This also require `funcall`s, since we return a `lambda` that doesn't live in -the function namespace. - -Like the Clojure one, it doesn't support optional parameters, `&rest` rest -arguments, docstrings, etc., but it also could evolve to do so. |