LINQ勉強会 (http://atnd.org/events/39864) で書いたもの

LinqStudy.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace LinqStudy
{
    public class LinqStudy
    {
        public static int Euler1(int max)
        {
            return Enumerable.Range(0, max).Where(j => j % 3 == 0 || j % 5 == 0).Sum();
        }

        public static readonly double SqrtFive = Math.Sqrt(5.0);
        public static readonly double Phi = (1.0 + SqrtFive) / 2.0;

        private static IEnumerable<int> Infinite()
        {
            var value = 0;
            while (true)
                yield return value++;
        }

        public static int Euler2(int limit)
        {
            return Infinite()
                .Select(i => (int)Math.Floor(Math.Pow(Phi, i) / SqrtFive + 0.5))
                .Where(i => i % 2 == 0)
                .TakeWhile(i => i < limit)
                .Sum();
        }
    }
}

LinqStudy.fs

module LinqStudy

open System

let euler1 num =
  [ 0 .. num - 1 ]
  |> List.filter (fun x -> x % 3 = 0 || x % 5 = 0)
  |> List.sum 

let sqrtFive = sqrt 5.0
let phi = (1.0 + sqrtFive) / 2.0

let infiniteIntSeq = Seq.unfold (fun i -> Some(i + 1, i + 1)) 0 |> Seq.cache

let euler2 limit =
  infiniteIntSeq
  |> Seq.map(fun x -> pown phi x / sqrtFive + 0.5 |> floor |> int)
  |> Seq.filter (fun x -> x % 2 = 0)
  |> Seq.takeWhile (fun x -> x < limit)
  |> Seq.sum

LinqStudytest.cs

// using MSTest and ChainingAssetion
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace LinqStury
{
    [TestClass]
    public class LinqStudyTest
    {
        [TestMethod]
        public void Euler1のテスト()
        {
            LinqStudy.LinqStudy.Euler1(1000).Is(233168);
        }

        [TestMethod]
        public void Euler2のテスト()
        {
            LinqStudy.LinqStudy.Euler2(4000000).Is(4613732);
        }
    }
}

LinqStudyTest.fs

// use FsUnit
module LinqStudy.Test

open NUnit.Framework
open FsUnit
open LinqStudy

[<Test>]
let ``Euler1のテスト``() =
  euler1 1000 |> should equal 233168

[<Test>]
let ``Euler2のテスト``() =
  euler2 4000000 |> should equal 4613732