private static IEnumerable <TSource> ExceptImpl <TSource>(this IEnumerable <TSource> first, IEnumerable <TSource> second, IEqualityComparer <TSource> comparer)
{
var hashSetFromFirstSequence = new HashSet <TSource>(second, comparer);
return(first.SelectMany(element =>
hashSetFromFirstSequence.Add(element) ?
SelectManyEnumerable.Repeat(element, 1) :
SelectManyEnumerable.Empty <TSource>()));
}
static void Main(string[] args)
{
var enumerable = SelectManyEnumerable.Range(1, 10);
var a = SelectManyEnumerable.Count(enumerable);
var first = SelectManyEnumerable.Range(1, 5);
var second = SelectManyEnumerable.Range(1, 3);
var concat = SelectManyEnumerable.Concat(first, second);
var except = first.Except(second).ToArray();
Console.WriteLine("Hello World!");
}
public static IEnumerable <TSource> Where <TSource>(this IEnumerable <TSource> source, Func <TSource, bool> predicate)
{
return(source.SelectMany(elem => predicate(elem) ?
SelectManyEnumerable.Repeat(elem, 1) :
SelectManyEnumerable.Empty <TSource>()));
}
public static IEnumerable <TResult> Select <TSource, TResult>(this IEnumerable <TSource> source, Func <TSource, TResult> selector)
{
return(source.SelectMany(elem => SelectManyEnumerable.Repeat(selector(elem), 1)));
}