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Merged
stephentoub merged 2 commits into from
Jun 18, 2025
Merged

Update Enumerable.Sequence based on post-merge feedback #116793

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a10100c
Update Enumerable.Sequence based on post-merge feedback
stephentoub Jun 18, 2025
6d67635
Add exception docs
stephentoub Jun 18, 2025
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72 changes: 45 additions & 27 deletions src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/Sequence.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,15 +11,18 @@ namespace System.Linq
{
public static partial class AsyncEnumerable
{
/// <summary>Generates a sequence that begins with <paramref name="start"/> and yields additional values each incremented by <paramref name="step"/> until <paramref name="endInclusive"/> is reached.</summary>
/// <summary>Generates a sequence that begins with <paramref name="start"/> and yields additional values each incremented by <paramref name="step"/> until <paramref name="endInclusive"/> is reached.</summary>
/// <typeparam name="T">The type of the value to be yielded in the result sequence.</typeparam>
/// <param name="start">The starting value. This value will always be included in the resulting sequence.</param>
/// <param name="endInclusive">The ending bound beyond which values will not be included in the sequence.</param>
/// <param name="step">The amount by which the next value in the sequence should be incremented from the previous value.</param>
/// <returns>An <see cref="IAsyncEnumerable{T}"/> that contains the sequence.</returns>
/// <exception cref="ArgumentNullException"><paramref name="start"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="step"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="endInclusive"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="step"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="start"/> is NaN.</exception>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="endInclusive"/> is NaN.</exception>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="step"/> is NaN.</exception>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="step"/> is greater than zero but <paramref name="endInclusive"/> is less than <paramref name="start"/>.</exception>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="step"/> is less than zero but <paramref name="endInclusive"/> is greater than <paramref name="start"/>.</exception>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="step"/> is zero and <paramref name="endInclusive"/> does not equal <paramref name="start"/>.</exception>
Expand All @@ -30,17 +33,43 @@ public static IAsyncEnumerable<T> Sequence<T>(T start, T endInclusive, T step) w
ThrowHelper.ThrowArgumentNullException(nameof(start));
}

if (T.IsNaN(start))
{
ThrowHelper.ThrowArgumentOutOfRangeException(nameof(start));
}

if (endInclusive is null)
{
ThrowHelper.ThrowArgumentNullException(nameof(endInclusive));
}

if (T.IsNaN(endInclusive))
{
ThrowHelper.ThrowArgumentOutOfRangeException(nameof(endInclusive));
}

if (step is null)
{
ThrowHelper.ThrowArgumentNullException(nameof(step));
}

if (step > T.Zero)
if (T.IsNaN(step))
{
ThrowHelper.ThrowArgumentOutOfRangeException(nameof(step));
}

if (T.IsZero(step))
{
// step == 0. If start != endInclusive, then the sequence would be infinite. As such, we validate
// that they're equal, and if they are, we return a sequence that yields the start/endInclusive value once.
if (start != endInclusive)
{
ThrowHelper.ThrowArgumentOutOfRangeException(nameof(step));
}

return Repeat(start, 1);
}
else if (T.IsPositive(step))
{
// Presumed to be the most common case, step > 0. Validate that endInclusive >= start, as otherwise we can't easily
// guarantee that the sequence will terminate.
Expand All @@ -52,7 +81,7 @@ public static IAsyncEnumerable<T> Sequence<T>(T start, T endInclusive, T step) w
// Otherwise, just produce an incrementing sequence.
return IncrementingIterator(start, endInclusive, step);
}
else if (step < T.Zero)
else
{
// step < 0. Validate that endInclusive <= start, as otherwise we can't easily guarantee that the sequence will terminate.
if (endInclusive > start)
Expand All @@ -63,31 +92,20 @@ public static IAsyncEnumerable<T> Sequence<T>(T start, T endInclusive, T step) w
// Then produce the decrementing sequence.
return DecrementingIterator(start, endInclusive, step);
}
else
{
// step == 0. If start != endInclusive, then the sequence would be infinite. As such, we validate
// that they're equal, and if they are, we return a sequence that yields the start/endInclusive value once.
if (start != endInclusive)
{
ThrowHelper.ThrowArgumentOutOfRangeException(nameof(step));
}

return Repeat(start, 1);
}

static async IAsyncEnumerable<T> IncrementingIterator(T start, T endInclusive, T step)
static async IAsyncEnumerable<T> IncrementingIterator(T current, T endInclusive, T step)
{
Debug.Assert(step > T.Zero);

yield return start;
yield return current;

while (true)
{
T next = start + step;
T next = current + step;

if (next >= endInclusive || next <= start)
if (next >= endInclusive || next <= current) // handle overflow and saturation
{
if (next == endInclusive && start != next)
if (next == endInclusive && current != next)
{
yield return next;
}
Expand All @@ -96,24 +114,24 @@ static async IAsyncEnumerable<T> IncrementingIterator(T start, T endInclusive, T
}

yield return next;
start = next;
current = next;
}
}


static async IAsyncEnumerable<T> DecrementingIterator(T start, T endInclusive, T step)
static async IAsyncEnumerable<T> DecrementingIterator(T current, T endInclusive, T step)
{
Debug.Assert(step < T.Zero);

yield return start;
yield return current;

while (true)
{
T next = start + step;
T next = current + step;

if (next <= endInclusive || next >= start)
if (next <= endInclusive || next >= current) // handle overflow and saturation
{
if (next == endInclusive && start != next)
if (next == endInclusive && current != next)
{
yield return next;
}
Expand All @@ -122,7 +140,7 @@ static async IAsyncEnumerable<T> DecrementingIterator(T start, T endInclusive, T
}

yield return next;
start = next;
current = next;
}
}
}
Expand Down
14 changes: 9 additions & 5 deletions src/libraries/System.Linq.AsyncEnumerable/tests/SequenceTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,11 +13,15 @@ namespace System.Linq.Tests
public class SequenceTests : AsyncEnumerableTests
{
[Fact]
public void NullArguments_Throws()
public void InvalidArguments_Throws()
{
AssertExtensions.Throws<ArgumentNullException>("start", () => AsyncEnumerable.Sequence((ReferenceAddable)null!, new(1), new(2)));
AssertExtensions.Throws<ArgumentNullException>("endInclusive", () => AsyncEnumerable.Sequence(new(1), (ReferenceAddable)null!, new(2)));
AssertExtensions.Throws<ArgumentNullException>("step", () => AsyncEnumerable.Sequence(new(1), new(2), (ReferenceAddable)null!));

AssertExtensions.Throws<ArgumentOutOfRangeException>("start", () => AsyncEnumerable.Sequence(float.NaN, 1.0f, 1.0f));
AssertExtensions.Throws<ArgumentOutOfRangeException>("endInclusive", () => AsyncEnumerable.Sequence(1.0f, float.NaN, 1.0f));
AssertExtensions.Throws<ArgumentOutOfRangeException>("step", () => AsyncEnumerable.Sequence(1.0f, 1.0f, float.NaN));
}

[Fact]
Expand Down Expand Up @@ -251,16 +255,16 @@ private sealed class ReferenceAddable(int value) : INumber<ReferenceAddable>
public static bool IsImaginaryNumber(ReferenceAddable value) => throw new NotImplementedException();
public static bool IsInfinity(ReferenceAddable value) => throw new NotImplementedException();
public static bool IsInteger(ReferenceAddable value) => throw new NotImplementedException();
public static bool IsNaN(ReferenceAddable value) => throw new NotImplementedException();
public static bool IsNegative(ReferenceAddable value) => throw new NotImplementedException();
public static bool IsNaN(ReferenceAddable value) => false;
public static bool IsNegative(ReferenceAddable value) => false;
public static bool IsNegativeInfinity(ReferenceAddable value) => throw new NotImplementedException();
public static bool IsNormal(ReferenceAddable value) => throw new NotImplementedException();
public static bool IsOddInteger(ReferenceAddable value) => throw new NotImplementedException();
public static bool IsPositive(ReferenceAddable value) => throw new NotImplementedException();
public static bool IsPositive(ReferenceAddable value) => false;
public static bool IsPositiveInfinity(ReferenceAddable value) => throw new NotImplementedException();
public static bool IsRealNumber(ReferenceAddable value) => throw new NotImplementedException();
public static bool IsSubnormal(ReferenceAddable value) => throw new NotImplementedException();
public static bool IsZero(ReferenceAddable value) => throw new NotImplementedException();
public static bool IsZero(ReferenceAddable value) => false;
public static ReferenceAddable MaxMagnitude(ReferenceAddable x, ReferenceAddable y) => throw new NotImplementedException();
public static ReferenceAddable MaxMagnitudeNumber(ReferenceAddable x, ReferenceAddable y) => throw new NotImplementedException();
public static ReferenceAddable MinMagnitude(ReferenceAddable x, ReferenceAddable y) => throw new NotImplementedException();
Expand Down
72 changes: 45 additions & 27 deletions src/libraries/System.Linq/src/System/Linq/Sequence.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,15 +11,18 @@ namespace System.Linq
{
public static partial class Enumerable
{
/// <summary>Generates a sequence that begins with <paramref name="start"/> and yields additional values each incremented by <paramref name="step"/> until <paramref name="endInclusive"/> is reached.</summary>
/// <summary>Generates a sequence that begins with <paramref name="start"/> and yields additional values each incremented by <paramref name="step"/> until <paramref name="endInclusive"/> is reached.</summary>
/// <typeparam name="T">The type of the value to be yielded in the result sequence.</typeparam>
/// <param name="start">The starting value. This value will always be included in the resulting sequence.</param>
/// <param name="endInclusive">The ending bound beyond which values will not be included in the sequence.</param>
/// <param name="step">The amount by which the next value in the sequence should be incremented from the previous value.</param>
/// <returns>An <see cref="IEnumerable{T}"/> that contains the sequence.</returns>
/// <exception cref="ArgumentNullException"><paramref name="start"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="step"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="endInclusive"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentNullException"><paramref name="step"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="start"/> is NaN.</exception>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="endInclusive"/> is NaN.</exception>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="step"/> is NaN.</exception>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="step"/> is greater than zero but <paramref name="endInclusive"/> is less than <paramref name="start"/>.</exception>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="step"/> is less than zero but <paramref name="endInclusive"/> is greater than <paramref name="start"/>.</exception>
/// <exception cref="ArgumentOutOfRangeException"><paramref name="step"/> is zero and <paramref name="endInclusive"/> does not equal <paramref name="start"/>.</exception>
Expand All @@ -30,17 +33,43 @@ public static IEnumerable<T> Sequence<T>(T start, T endInclusive, T step) where
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.start);
}

if (T.IsNaN(start))
{
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.start);
}

if (endInclusive is null)
{
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.endInclusive);
}

if (T.IsNaN(endInclusive))
{
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.endInclusive);
}

if (step is null)
{
ThrowHelper.ThrowArgumentNullException(ExceptionArgument.step);
}

if (step > T.Zero)
if (T.IsNaN(step))
{
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.step);
}

if (T.IsZero(step))
{
// If start != endInclusive, then the sequence would be infinite. As such, we validate
// that they're equal, and if they are, we return a sequence that yields the start/endInclusive value once.
if (start != endInclusive)
{
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.step);
}

return Repeat(start, 1);
}
else if (T.IsPositive(step))
{
// Presumed to be the most common case, step > 0. Validate that endInclusive >= start, as otherwise we can't easily
// guarantee that the sequence will terminate.
Expand All @@ -67,7 +96,7 @@ public static IEnumerable<T> Sequence<T>(T start, T endInclusive, T step) where
// Otherwise, just produce an incrementing sequence.
return IncrementingIterator(start, endInclusive, step);
}
else if (step < T.Zero)
else
{
// step < 0. Validate that endInclusive <= start, as otherwise we can't easily guarantee that the sequence will terminate.
if (endInclusive > start)
Expand All @@ -78,17 +107,6 @@ public static IEnumerable<T> Sequence<T>(T start, T endInclusive, T step) where
// Then produce the decrementing sequence.
return DecrementingIterator(start, endInclusive, step);
}
else
{
// step == 0. If start != endInclusive, then the sequence would be infinite. As such, we validate
// that they're equal, and if they are, we return a sequence that yields the start/endInclusive value once.
if (start != endInclusive)
{
ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument.step);
}

return Repeat(start, 1);
}

static RangeIterator<T>? TryUseRange<TLarger>(T start, T endInclusive, T step, TLarger maxValue) where TLarger : INumber<TLarger>
{
Expand All @@ -101,19 +119,19 @@ public static IEnumerable<T> Sequence<T>(T start, T endInclusive, T step) where
return null;
}

static IEnumerable<T> IncrementingIterator(T start, T endInclusive, T step)
static IEnumerable<T> IncrementingIterator(T current, T endInclusive, T step)
{
Debug.Assert(step > T.Zero);

yield return start;
yield return current;

while (true)
{
T next = start + step;
T next = current + step;

if (next >= endInclusive || next <= start)
if (next >= endInclusive || next <= current) // handle overflow and saturation
{
if (next == endInclusive && start != next)
if (next == endInclusive && current != next)
{
yield return next;
}
Expand All @@ -122,24 +140,24 @@ static IEnumerable<T> IncrementingIterator(T start, T endInclusive, T step)
}

yield return next;
start = next;
current = next;
}
}


static IEnumerable<T> DecrementingIterator(T start, T endInclusive, T step)
static IEnumerable<T> DecrementingIterator(T current, T endInclusive, T step)
{
Debug.Assert(step < T.Zero);

yield return start;
yield return current;

while (true)
{
T next = start + step;
T next = current + step;

if (next <= endInclusive || next >= start)
if (next <= endInclusive || next >= current) // handle overflow and saturation
{
if (next == endInclusive && start != next)
if (next == endInclusive && current != next)
{
yield return next;
}
Expand All @@ -148,7 +166,7 @@ static IEnumerable<T> DecrementingIterator(T start, T endInclusive, T step)
}

yield return next;
start = next;
current = next;
}
}
}
Expand Down
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