/// <summary>
/// Prepends a single value to a sequence.
/// </summary>
/// <typeparam name="TSource">The type of the elements of <paramref name="source" />.</typeparam>
/// <param name="source">The sequence to prepend to.</param>
/// <param name="value">The value to prepend.</param>
/// <returns>
/// Returns a sequence where a value is prepended to it.
/// </returns>
/// <remarks>
/// This operator uses deferred execution and streams its results.
/// </remarks>
/// <code>
/// int[] numbers = { 1, 2, 3 };
/// IEnumerable<int> result = numbers.Prepend(0);
/// </code>
/// The
/// <c>result</c>
/// variable, when iterated over, will yield
/// 0, 1, 2 and 3, in turn.
public static IEnumerable <TSource> Prepend <TSource>(this IEnumerable <TSource> source, TSource value)
{
if (source == null)
{
throw new ArgumentNullException("source");
}
return(LinqEnumerable.Repeat(value, 1).Concat(source));
}
/// <summary>
/// Returns a sequence consisting of the head elements and the given tail element.
/// </summary>
/// <typeparam name="T">Type of sequence</typeparam>
/// <param name="head">All elements of the head. Must not be null.</param>
/// <param name="tail">Tail element of the new sequence.</param>
/// <returns>A sequence consisting of the head elements and the given tail element.</returns>
/// <remarks>This operator uses deferred execution and streams its results.</remarks>
public static IEnumerable <T> Concat <T>(this IEnumerable <T> head, T tail)
{
if (head == null)
{
throw new ArgumentNullException("head");
}
return(head.Concat(LinqEnumerable.Repeat(tail, 1)));
}
public void YieldTests()
{
int i = 1;
Assert.True(LinqEnumerable.Yield(i).SequenceEqual(new[] { 1 }));
}
public void Repeat()
{
Assert.True(LinqEnumerable.Repeat(1u, 3u).SequenceEqual(new[] { 1u, 1u, 1u }));
}
public void RangeUshort()
{
Assert.True(LinqEnumerable.RangeUshort(5).SequenceEqual(new ushort[] { 0, 1, 2, 3, 4 }));
}
public void Yield_Prepend_Append()
{
Assert.True(LinqEnumerable.Yield(3).Prepend(2).Append(4).SequenceEqual(new[] { 2, 3, 4 }));
}
