archived-discord-bot/CompatBot/Utils/EnumerableExtensions.cs

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

namespace CompatBot.Utils
{
    public static class EnumerableExtensions
    {
        public static IEnumerable<TResult> Pairwise<T, TResult>(this IEnumerable<T> source, Func<T, T, TResult> selector)
        {
            if (source == null)
                throw new ArgumentNullException(nameof(source));

            if (selector == null)
                throw new ArgumentNullException(nameof(selector));

            using (var e = source.GetEnumerator())
            {
                if (!e.MoveNext())
                    yield break;

                T prev = e.Current;
                if (!e.MoveNext())
                    yield break;

                do
                {
                    yield return selector(prev, e.Current);
                    prev = e.Current;
                } while (e.MoveNext());
            }
        }

        public static IEnumerable<T> Single<T>(T item)
        {
            yield return item;
        }
    }
}