Add MemoryExtensions.Min/Max#128306
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Pull request overview
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Adds Min and Max extension methods on ReadOnlySpan<T> (with optional IComparer<T>), mirroring LINQ's Enumerable.Min/Max semantics for spans. Includes ref assembly updates and tests.
Changes:
- New
Min/MaxReadOnlySpan extension methods with empty-span and null-element handling. - Reference assembly exposes the four new API overloads.
- New test file covering empty, all-null, mixed-null, default comparer, and custom comparer scenarios.
Reviewed changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 8 comments.
| File | Description |
|---|---|
| src/libraries/System.Private.CoreLib/src/System/MemoryExtensions.cs | Implements Min/Max with a generic comparer fast path and null-skipping inner core. |
| src/libraries/System.Memory/ref/System.Memory.cs | Adds public surface for the four new overloads. |
| src/libraries/System.Memory/tests/System.Memory.Tests.csproj | Includes the new test file. |
| src/libraries/System.Memory/tests/ReadOnlySpan/MinMax.cs | Tests for empty/null/normal/custom-comparer behaviors. |
| return default; | ||
| } | ||
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| ThrowHelper.ThrowInvalidOperationException(); |
| /// <param name="comparer">The <see cref="IComparer{T}"/> to compare values.</param> | ||
| /// <returns>The minimum value in the span.</returns> | ||
| /// <exception cref="InvalidOperationException"><paramref name="span"/> is empty and <typeparamref name="T"/> is a non-nullable value type.</exception> | ||
| public static T? Min<T>(this ReadOnlySpan<T> span, IComparer<T> comparer) |
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| T next = span[i]; | ||
| if (next is not null && comparer.Compare(next, value) < 0) |
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| static T? MinCore<TComparer>(ReadOnlySpan<T> span, TComparer comparer) | ||
| where TComparer : IComparer<T> |
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| Min(span, comparer: null!); | ||
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| /// <summary> | ||
| /// Returns the minimum value in the span. | ||
| /// </summary> | ||
| /// <typeparam name="T">The type of the elements in the span.</typeparam> | ||
| /// <param name="span">The span of values to determine the minimum value of.</param> | ||
| /// <param name="comparer">The <see cref="IComparer{T}"/> to compare values.</param> | ||
| /// <returns>The minimum value in the span.</returns> | ||
| /// <exception cref="InvalidOperationException"><paramref name="span"/> is empty and <typeparamref name="T"/> is a non-nullable value type.</exception> | ||
| public static T? Min<T>(this ReadOnlySpan<T> span, IComparer<T> comparer) |
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| public static void MinMax_CustomComparer_IsUsed() | ||
| { | ||
| ReadOnlySpan<int> ints = new int[] { 4, -1, 7, 2 }; | ||
| IComparer<int> reverse = Comparer<int>.Create((left, right) => right.CompareTo(left)); |
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| public static T? Max<T>(this System.ReadOnlySpan<T> span, System.Collections.Generic.IComparer<T> comparer) { throw null; } | ||
| public static T? Min<T>(this System.ReadOnlySpan<T> span) { throw null; } | ||
| public static T? Min<T>(this System.ReadOnlySpan<T> span, System.Collections.Generic.IComparer<T> comparer) { throw null; } | ||
| [System.Runtime.CompilerServices.OverloadResolutionPriorityAttribute(-1)] |
| /// <typeparam name="T">The type of the elements in the span.</typeparam> | ||
| /// <param name="span">The span of values to determine the minimum value of.</param> | ||
| /// <returns>The minimum value in the span.</returns> | ||
| /// <exception cref="InvalidOperationException"><paramref name="span"/> is empty and <typeparamref name="T"/> is a non-nullable value type.</exception> |
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This pull request adds new
MinandMaxextension methods forReadOnlySpan<T>to theSystem.Memorylibrary, allowing users to efficiently find the minimum and maximum values in a span, optionally using a custom comparer. Comprehensive unit tests are included to verify correct behavior for various data types and edge cases.New
MinandMaxmethods forReadOnlySpan<T>:Min<T>andMax<T>extension methods toMemoryExtensionsforReadOnlySpan<T>, supporting both default and custom comparers, and handling nullable and reference types gracefully. These methods throw an exception on empty spans of non-nullable value types and returnnullfor empty spans of reference or nullable types. [1] [2]Unit tests:
ReadOnlySpan/MinMax.csto cover empty spans, all-null values, custom comparers, and typical scenarios for both value and reference types.System.Memory.Tests.csprojto ensure the tests are run as part of the test suite.Fixes #127083