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I am using docjure and it needs a column map for the select-columns function. I would like to capture all my columns without manually specifying it. How to generate the following as a lazy infinite vector sequence [: A: B: C: D: E ...: AA: AB: AC ....: ZZ ...: XFD]?

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Your question boils down to the following: "How to convert a number to a base-26 string with the alphabet AZ?"

Here one of the ways to do this is probably not the most concise way, but to make it more elegant remains as an exercise for the reader :).

, 0-25 "A" - "Z", 26 - "AA" .. to-col, column. .

(defn to-col [num]
  (loop [n num s ()]
    (if (> n 25)
      (let [r (mod n 26)]
        (recur (dec (/ (- n r) 26)) (cons (char (+ 65 r)) s)))
      (keyword (apply str (cons (char (+ 65 n)) s))))))

:

(take 100 (map to-col (range)))
;; => (:A :B :C :D :E :F :G :H :I :J :K :L :M :N :O :P :Q :R :S :T :U :V :W
;; :X :Y :Z :AA :AB :AC :AD :AE :AF :AG :AH :AI :AJ :AK :AL :AM :AN :AO :AP
;; :AQ :AR :AS :AT :AU :AV :AW :AX :AY :AZ :BA :BB :BC :BD :BE :BF :BG :BH
;; :BI :BJ :BK :BL :BM :BN :BO :BP :BQ :BR :BS :BT :BU :BV :BW :BX :BY :BZ
;; :CA :CB :CC :CD :CE :CF :CG :CH :CI :CJ :CK :CL :CM :CN :CO :CP :CQ :CR
;; :CS :CT :CU :CV)
+6

clojure corecursion ( " " , ?) :

(def abc (map (comp str char) (range 65 91)))
(defn cols [seed]
  (let [next #(for [x %] (for [y seed] (str x y)))]
    (->> (iterate #(apply concat (next %)) seed)
         (mapcat identity))))

(time (first (drop 475254 (cols abc))))
"Elapsed time: 356.879148 msecs"
"AAAAA"

(doc iterate)
-------------------------
clojure.core/iterate
([f x])
  Returns a lazy sequence of x, (f x), (f (f x)) etc. f must be free of side-effects

EDIT: ""

(defn ordered-combinations [seed]
  (->> (map list seed)
       (iterate #(for [x % y seed] (concat x [y])))
       (mapcat identity)))

(def cols
  (let [abc (map char (range 65 91))]
    (map #(apply str %) (ordered-combinations abc))))

user> (take 30  (map #(apply str %) cols))
("A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T" "U" "V" "W" "X" "Y" "Z" "AA" "AB" "AC" "AD")
user> (take 28 (ordered-combinations [0 1]))
((0) (1) (0 0) (0 1) (1 0) (1 1) (0 0 0) (0 0 1) (0 1 0) (0 1 1) (1 0 0) (1 0 1) (1 1 0) (1 1 1) (0 0 0 0) (0 0 0 1) (0 0 1 0) (0 0 1 1) (0 1 0 0) (0 1 0 1) (0 1 1 0) (0 1 1 1) (1 0 0 0) (1 0 0 1) (1 0 1 0) (1 0 1 1) (1 1 0 0) (1 1 0 1))
+4

; , .

, , .

(take 40 (map #(keyword (apply str %)) 
           (rest (combinatorics/subsets  "ABCDEFGHIJKLMNOPQRSTUVWXYZ"))))
(:A :B :C :D :E :F :G :H :I :J :K :L :M :N
 :O :P :Q :R :S :T :U :V :W :X :Y :Z :AB :AC 
 :AD :AE :AF :AG :AH :AI :AJ :AK :AL :AM :AN :AO)

foo.core> (nth (map #(keyword (apply str %)) 
                 (rest (combinatorics/subsets  "ABCDEFGHIJKLMNOPQRSTUVWXYZ"))) 
               40000)
:BLOUZ

project.clj:

(defproject foo "1.0.0-SNAPSHOT"
  :description "FIXME: write description"
  :dependencies [[org.clojure/clojure "1.3.0"]
                 [ org.clojure/math.combinatorics "0.0.3"]]
  :dev-dependencies [[swank-clojure/swank-clojure "1.4.0"]]) ; swank)

math.combanatorics:

(ns foo.core
  (:require [clojure.math.combinatorics :as combinatorics]))
+2

, jneira iterate .

, , . , , loop/recur:

(defn column-names-seq [alphabet]
  (->> (map str alphabet)
     (iterate (fn [chars]
                (for [x chars
                      y alphabet]
                  (str x y))))
     (apply concat)))

, , :

(take 30 (column-names-seq "ABCDEFGHIJKLMNOPQRSTUVWXYZ"))  ;; => ("A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T" "U" "V" "W" "X" "Y" "Z" "AA" "AB" "AC" "AD")
+2

, , ( , , , , : o).

(defn stream [seed]
  (defn helper [slow]
    (concat (map #(str (first slow) %) seed) (lazy-seq (helper (rest slow)))))
  (declare delayed)
  (let [slow (cons "" (lazy-seq delayed))]
    (def delayed (helper slow))
    delayed))

(take 25 (stream ["a" "b" "c"]))
("a" "b" "c" "aa" "ab" "ac" "ba" "bb" "bc" "ca" "cb" "cc" "aaa" "aab" "aac" "aba" "abb" "abc" "aca" "acb" "acc" "baa" "bab" "bac" "bba")

git. , def , .

: . ( ) , . , ( "", , , - ).

" " Haskell. Clojure, ( "" ) - , , def ( , - delay force, ).

, ?

[ 2012-07-19 ]

Clojure: (, ) ? ( jneira).

, iterate:

(defn stream [seed]
  (defn helper [slow] (mapcat (fn [c] (map #(str c %) seed)) slow))
  (apply concat (iterate helper seed)))
+1

, "", -, :

(def all-letters (map char (range 65 90)))
(defn kw [& args] (keyword (apply str args)))
(concat
  (for [l all-letters] (kw l))
  (for [l all-letters l2 all-letters] (kw l l2))
  (for [l all-letters l2 all-letters l3 all-letters] (kw l l2 l3)))
0
#include<stdio.h>
int main()
{
int n=703;

char arr[26]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};

while(n){
printf("%c ",arr[(n)%26]);
n=(n)/26;

}
return 0;
}

, , , - ... , , , ...

-1

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