kohyama

Clojure tips infrequently used

To get names of methods of a class

(map #(.getName %) (.getMethods java.io.File))
; -> ("equals" "toString" "hashCode" "compareTo" "compareTo" "getName" "length" "getParent" "isAbsolute" "getCanonicalPath" "setReadOnly" "list" "list" "delete" "getParentFile" "getPath" "getAbsolutePath" "getAbsoluteFile" "getCanonicalFile" "toURL" "toURI" "canRead" "canWrite" "exists" "isDirectory" "isFile" "isHidden" "lastModified" "createNewFile" "deleteOnExit" "listFiles" "listFiles" "listFiles" "mkdir" "mkdirs" "renameTo" "setLastModified" "setWritable" "setWritable" "setReadable" "setReadable" "setExecutable" "setExecutable" "canExecute" "listRoots" "getTotalSpace" "getFreeSpace" "getUsableSpace" "createTempFile" "createTempFile" "wait" "wait" "wait" "getClass" "notify" "notifyAll")

kohyama

(require '[clojure.test :refer (is)])

(defn in-words
  "Represents the given number in English words without spaces nor hyphens.
  This works with a number in the range from 1 to 1000"
  [n]
  (cond
    (< n 20)
      (["" "one" "two" "three" "four" "five" "six" "seven" "eight"
        "nine" "ten" "eleven" "twelve" "thirteen" "fourteen"

kohyama

(require '[clojure.test :refer (is)])

(defn pms
  "Permutations lexicographic by index."
  [[a & [b & [c & _]] :as ls]]
  (cond
    (nil? a) '()
    (nil? b) `(~a)
    (nil? c) `((~a ~b) (~b ~a))
    :else (mapcat (fn [h] (map (fn [r] (cons h r))

kohyama

(require '[clojure.string :as s])
(require '[clojure.test :refer (deftest run-tests is)])
 
(defn trans [[& rows]] (apply (partial map list) rows))
 
(defn flip [mat] (map reverse mat))
 
(defn rot45 [mat]
  (let [w (count (first mat))
        h (count mat)

kohyama

;; 閏年かどうか
(defn leap? [year]
  (and (zero? (mod year 4))
       (or (pos? (mod year 100))
           (zero? (mod year 400)))))

;; 西暦で与えられた年の各月の日数のリスト
(defn numbers-of-days [year]
  (if (leap? year)
     ;;Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

kohyama

(require '[clojure.test :refer (is)])
(require '[clojure.string :as s])

(def input "
                            75
                          95  64
                        17  47  82
                      18  35  87  10
                    20  04  82  47  65
                  19  01  23  75  03  34

kohyama

#include <stdio.h>
#include <stdlib.h>

#define u16 unsigned short
#define u8 unsigned char

static u16
crc16(u8 *p, int n)
{
  static const u16 wCRCTable[] = {

kohyama

;;; Copyright (c) 2013 Yoshinori Kohyama. Distributed under the BSD 3-Clause License.
(ns puyo
  (:require [clojure.test :refer (with-test run-tests are)]
            [clojure.set :refer (union)]
            [clojure.string :as string]))

(with-test
  (defn- fall-one [b s]
    (->> (reverse b)
      (apply map vector)

kohyama

ファンクタ, アプリカティブ, モナド

はじめに

「そもそも概念が分からない」という方に向けた説明です.
簡略化のため大幅に説明を省略しています. ご容赦ください.
誤りは御指摘いただければ幸いです.

「ファンクタ」, 「アプリカティブ」, 「モナド」 などは Haskell に限定された概念・用語ではありませんが,

kohyama

(require '[clojure.test :refer (with-test are run-tests)])

(with-test
  (defn str-drop-while-same [& args]
    (if (some nil? args) args
        (->> (map #(concat % (repeat nil)) args)
          (apply map vector)
          (drop-while #(apply = %))
          (take-while #(some identity %))
          (apply map str))))