Either.cs

using System;
using System.Collections.Generic;
using System.Linq;
using FluentAssertions;
using Xunit;
using LanguageExt;
using static LanguageExt.Prelude;

namespace LanguageExtDemo
{
    public class Either
    {
        [Fact]
        public void mapping_a_list_of_eithers_to_an_either_of_lists()
        {
            Assert.Equal(
                Right(List(1,2,3)), 
                List((Either<string,int>)Right(1), Right(2), Right(3)).Sequence());
            Assert.Equal(
                Left("error"), 
                List((Either<string,int>)Right(1), Right(2), Left("error"), Right(3)).Sequence());
        }

        [Fact]
        public void mapping_an_enumerable_of_eithers_to_an_either_of_enumerable()
        {
            Either<string,List<int>> result = new List<Either<string, int>> {Right(1), Right(2), Right(3)}
                .Aggregate(
                    (Either<string, List<int>>) Right(new List<int>()),
                    (ma, mb) =>
                        from a in ma
                        from b in mb
                        select a.Concat(new []{b}).ToList());
        }
    }
}