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;;;; cf. http://riktor.hatenablog.com/entry/2012/07/25/001118 | |
(first '(1 2 3)) | |
(first '((1 2 3) 4 5 6)) | |
(rest '(1 2 3)) | |
(rest '(1 2 (3 4 5))) | |
(cons 1 '(2 3)) | |
(cons '(1 2 3) '((4 5 6))) | |
(cons 1 nil) | |
(rest '(1)) | |
(rest nil) | |
(identical? nil ()) | |
(rest ()) | |
(defn my-nth-rest [n coll] | |
(if (or (empty? coll) (zero? n)) | |
coll | |
(recur (dec n) (rest coll)))) | |
(defn my-map [f coll] | |
(if (empty? coll) | |
() | |
(cons (f (first coll)) | |
(my-map f (rest coll))))) | |
(my-map (fn [x] (* x 2)) '(1 2 3)) | |
(my-map (fn [x] (- x 1)) '(1 2 3)) | |
(defn my-map-tailrec [f coll] | |
(letfn [(helper [coll acc] | |
(if (empty? coll) | |
(reverse acc) | |
(recur (rest coll) | |
(cons (f (first coll)) acc))))] | |
(helper coll ()))) | |
(defn my-append [coll1 coll2] | |
(if (empty? coll1) | |
coll2 | |
(cons (first coll1) | |
(my-append (rest coll1) coll2)))) | |
(defn my-append-tailrec [coll1 coll2] | |
(letfn [(rec [coll acc] | |
(if (empty? coll) | |
(concat (reverse acc) coll2) | |
(recur (rest coll) | |
(cons (first coll) acc))))] | |
(rec coll1 ()))) | |
(defn my-append-concat [coll1 coll2] | |
(concat coll1 coll2)) | |
(defn my-append-splicing [coll1 coll2] | |
`(~@coll1 ~@coll2)) | |
(defn my-append-cps [coll1 coll2] | |
(letfn [(rec [coll cont] | |
(if (empty? coll) | |
(cont coll2) | |
(recur (rest coll) | |
(fn [x] (cont (cons (first coll) x))))))] | |
(rec coll1 identity))) | |
(defn my-reverse [coll] | |
(letfn [(rec [coll acc] | |
(if (empty? coll) | |
acc | |
(recur (rest coll) | |
(cons (first coll) acc))))] | |
(rec coll ()))) |
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