Slice and dice baby

Slice.cs

  	public static IEnumerable<IEnumerable<TSource>> Slice<TSource>(
			this IEnumerable<TSource> sequence, 
			int maxItemsPerSlice)
		{
			if (maxItemsPerSlice <= 0)
			{
				throw new ArgumentOutOfRangeException("maxItemsPerSlice", "maxItemsPerSlice must be greater than 0");
			}

			var slice = new List<TSource>(maxItemsPerSlice);

			foreach (var item in sequence)
			{
				slice.Add(item);

				if (slice.Count == maxItemsPerSlice)
				{
					yield return slice.ToArray();
					slice = new List<TSource>(maxItemsPerSlice);
				}
			}

			// return the "crumbs" that 
			// didn't make it into a full slice
			if (slice.Count > 0)
			{
				yield return slice.ToArray();
			}
		}

		public static IEnumerable<IEnumerable<TResult>> Slice<TSource, TResult>(
			this IEnumerable<TSource> sequence, 
			int maxItemsPerSlice, 
			Func<TSource, TResult> selector)
		{
			if (maxItemsPerSlice <= 0)
			{
				throw new ArgumentOutOfRangeException("maxItemsPerSlice", "maxItemsPerSlice must be greater than 0");
			}

			var slice = new List<TResult>(maxItemsPerSlice);

			foreach (var item in sequence)
			{
				slice.Add(selector(item));

				if (slice.Count == maxItemsPerSlice)
				{
					yield return slice.ToArray();
					slice.Clear();
				}
			}

			// return the "crumbs" that 
			// didn't make it into a full slice
			if (slice.Count > 0)
			{
				yield return slice.ToArray();
			}
		}

Hey Jimmy, Michael found a bug in this Slice extension method.

Here is a test that reproduces the issue:

public void Should_slice_collection_without_side_effects()
{
    var list = new List<IEnumerable<int>>();

     var otherList = Enumerable.Range(0, 9);

     var result = otherList.Slice(3);

     list.AddRange(result);

     list.Count().ShouldEqual(3);

     var firstSlice = list[0];

     //This will fail, firstSlice will be an empty array
     firstSlice.ToArray().ShouldEqual(new[] { 0, 1, 2 });
 }

To fix it, create a new List instance and assign it to slice instead of calling slice.Clear();

HAPPY NOW?!?

👍

oops, spoke too soon, line 50 is still broken