cesare

module MaxSubseq (maxSubseq) where
import Prelude hiding (seq, sum)

data Seq = Seq { seq::[Double], sum::Double } deriving Show
instance Eq Seq where
  (Seq _ x) == (Seq _ y) = x == y

instance Ord Seq where
  (Seq _ x) <= (Seq _ y) = x <= y

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Enumerable 再訪

Enumarable って？

• 集合っぽいもののそれぞれの要素にいろいろできるやつ
• http://docs.ruby-lang.org/ja/2.2.0/class/Enumerable.html

よく使う Enumerable なメソッド

※分類は主観が入ってます

cesare

class Celebrity
  attr_reader :matrix

  def initialize(rows)
    @matrix = rows
  end

  def knows?(from, to)
    @matrix[from][to] == 1
  end

cesare

import Data.List ((\\))
import qualified Data.Map as Map

prune :: Ord k => Map.Map k k -> Map.Map k k
prune m = _prune m orphans
  where
    _prune m [] = m
    _prune m os = prune $ foldl (flip Map.delete) m os
    orphans = (Map.keys m) \\ (Map.elems m)

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defmodule Chapter5 do
  def polynomial2(as, x) do
    Stream.iterate(1, &(&1 * x))
      |> Enum.zip(as)
      |> Enum.map(fn {x, a} -> x * a end)
      |> Enum.sum
  end

  def polynomial3(as, x) do
    Enum.reverse(as) |> Enum.reduce(&(&2 * x + &1))

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社内勉強会 Elm 篇

Elm

• AltJS (？)
• 関数型
• Haskell っぽい構文
  • モナドとか出てこない
  • 遅延評価はない
• Reactive / FRP

cesare

require 'sudden_death'

module Lita
  module Handlers
    class Suddendeath < Handler
      route /^(突然の.*)/, :sudden_death, command: false

      def sudden_death(response)
        response.reply response.match_data[0].sudden_death
      end

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TAX_RATE = 1.08

# 「1.08 を掛けて→小数点以下を切り捨てる」という演算で target を超えない最大の数値を求める
# 戻値 [t: Fixnum, d: Fixnum, i: Fixnum, s: Fixnum]
#
#   t: 元々の税込み価格 (= target)
#   d: 求める税抜き価格
#   i: 計算結果の税抜き価格に税を乗せた価格
#   s: 差分 (t - i)
#

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// http://qiita.com/t_uda/items/1969e09a970d71e4cfd6

function hoge(x) {
    switch (true) {
    case x < 0:
        console.log(x + " は自然数ではありません．");
        break;
    case x === 0:
        console.log("ここでは 0 は自然数です．");
        break;

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# Example Answer to http://qiita.com/jnchito/items/c4a56046be1096c19b1c

def count_by_word(str)
  raise ArgumentError, 'str should be a string' unless str.is_a? String

  str.split.reduce(Hash.new(0)) {|rs, w| rs.merge(w => rs[w] + 1) }
end

describe "count_by_word" do
  let(:results) { count_by_word(string) }