MinBy and MaxBy Span

Author: dragon7307

src/Extensions/Span/SpanExtensions.Linq.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Numerics;
 
 namespace SpanExtensions
@@ -1111,5 +1112,71 @@ public static BigInteger Max<T>(this Span<T> source, Func<T, BigInteger> selecto
             return ReadOnlySpanExtensions.Max(source, selector);
         }
 #endif
+
+        /// <summary>
+        /// Returns the minimum value in a generic sequence according to a specified key selector function.
+        /// </summary>
+        /// <typeparam name="TSource">The type of elements in <paramref name="source"/>.</typeparam>
+        /// <typeparam name="TKey">The type of key to compare elements by.</typeparam>
+        /// <param name="source">A <see cref="Span{TSource}"/> to determine the minimum value of.</param>
+        /// <param name="keySelector">A function to extract the key for each element.</param>
+        /// <returns>The value with the minimum key in <paramref name="source"/>.</returns>
+        /// <exception cref="ArgumentNullException"><paramref name="keySelector"/> is null.</exception>
+        /// <exception cref="InvalidOperationException"><typeparamref name="TSource"/> is a primitive type and <paramref name="source"/> is empty.</exception>
+        /// <remarks>If <paramref name="source"/> is empty and <typeparamref name="TSource"/> is a non-nullable struct, such as a primitive type, an <see cref="InvalidOperationException"/> is thrown.</remarks>
+        public static TSource MinBy<TSource, TKey>(this Span<TSource> source, Func<TSource, TKey> keySelector) where TKey : IComparable<TKey>
+        {
+            return ReadOnlySpanExtensions.MinBy(source, keySelector);
+        }
+
+        /// <summary>
+        /// Returns the minimum value in a generic sequence according to a specified key selector function.
+        /// </summary>
+        /// <typeparam name="TSource">The type of elements in <paramref name="source"/>.</typeparam>
+        /// <typeparam name="TKey">The type of key to compare elements by.</typeparam>
+        /// <param name="source">A <see cref="Span{TSource}"/> to determine the minimum value of.</param>
+        /// <param name="keySelector">A function to extract the key for each element.</param>
+        /// <param name="comparer">The <see cref="IComparer{TSource}"/> to compare keys.</param>
+        /// <returns>The value with the minimum key in <paramref name="source"/>.</returns>
+        /// <exception cref="ArgumentNullException"><paramref name="keySelector"/> is null.</exception>
+        /// <exception cref="InvalidOperationException"><typeparamref name="TSource"/> is a primitive type and <paramref name="source"/> is empty.</exception>
+        /// <remarks>If <paramref name="source"/> is empty and <typeparamref name="TSource"/> is a non-nullable struct, such as a primitive type, an <see cref="InvalidOperationException"/> is thrown.</remarks>
+        public static TSource MinBy<TSource, TKey>(this Span<TSource> source, Func<TSource, TKey> keySelector, IComparer<TKey> comparer)
+        {
+            return ReadOnlySpanExtensions.MinBy(source, keySelector, comparer);
+        }
+
+        /// <summary>
+        /// Returns the maximum value in a generic sequence according to a specified key selector function.
+        /// </summary>
+        /// <typeparam name="TSource">The type of elements in <paramref name="source"/>.</typeparam>
+        /// <typeparam name="TKey">The type of key to compare elements by.</typeparam>
+        /// <param name="source">A <see cref="Span{TSource}"/> to determine the maximum value of.</param>
+        /// <param name="keySelector">A function to extract the key for each element.</param>
+        /// <returns>The value with the maximum key in <paramref name="source"/>.</returns>
+        /// <exception cref="ArgumentNullException"><paramref name="keySelector"/> is null.</exception>
+        /// <exception cref="InvalidOperationException"><typeparamref name="TSource"/> is a primitive type and <paramref name="source"/> is empty.</exception>
+        /// <remarks>If <paramref name="source"/> is empty and <typeparamref name="TSource"/> is a non-nullable struct, such as a primitive type, an <see cref="InvalidOperationException"/> is thrown.</remarks>
+        public static TSource MaxBy<TSource, TKey>(this Span<TSource> source, Func<TSource, TKey> keySelector) where TKey : IComparable<TKey>
+        {
+            return ReadOnlySpanExtensions.MaxBy(source, keySelector);
+        }
+
+        /// <summary>
+        /// Returns the maximum value in a generic sequence according to a specified key selector function.
+        /// </summary>
+        /// <typeparam name="TSource">The type of elements in <paramref name="source"/>.</typeparam>
+        /// <typeparam name="TKey">The type of key to compare elements by.</typeparam>
+        /// <param name="source">A <see cref="Span{TSource}"/> to determine the maximum value of.</param>
+        /// <param name="keySelector">A function to extract the key for each element.</param>
+        /// <param name="comparer">The <see cref="IComparer{TSource}"/> to compare keys.</param>
+        /// <returns>The value with the maximum key in <paramref name="source"/>.</returns>
+        /// <exception cref="ArgumentNullException"><paramref name="keySelector"/> is null.</exception>
+        /// <exception cref="InvalidOperationException"><typeparamref name="TSource"/> is a primitive type and <paramref name="source"/> is empty.</exception>
+        /// <remarks>If <paramref name="source"/> is empty and <typeparamref name="TSource"/> is a non-nullable struct, such as a primitive type, an <see cref="InvalidOperationException"/> is thrown.</remarks>
+        public static TSource MaxBy<TSource, TKey>(this Span<TSource> source, Func<TSource, TKey> keySelector, IComparer<TKey> comparer)
+        {
+            return ReadOnlySpanExtensions.MaxBy(source, keySelector, comparer);
+        }
     }
 }