added Count; Where; AsEnumerable.

Author: dragon7307

src/Extensions/ReadOnlySpan/Linq/AsEnumerable.cs

@@ -0,0 +1,24 @@
+using System;
+using System.Collections.Generic;
+
+namespace SpanExtensions
+{
+    public static partial class ReadOnlySpanExtensions
+    {
+        /// <summary>
+        /// Returns the input typed as <see cref="IEnumerable{T}"/>.
+        /// </summary>
+        /// <param name="source">The sequence to type as <see cref="IEnumerable{T}"/>.</param>
+        /// <typeparam name="T">The type of elements in <paramref name="source"/>.</typeparam>
+        /// <returns>The input sequence typed as <see cref="IEnumerable{T}"/>.</returns>
+        public static IEnumerable<T> AsEnumerable<T>(this ReadOnlySpan<T> source)
+        {
+            ReadOnlySpan<T>.Enumerator e = source.GetEnumerator();
+
+            while(e.MoveNext())
+            {
+                yield return e.Current;
+            }
+        }
+    }
+}

src/Extensions/ReadOnlySpan/Linq/Count.cs

@@ -0,0 +1,51 @@
+using System;
+
+namespace SpanExtensions
+{
+    public static partial class ReadOnlySpanExtensions
+    {
+        /// <summary>
+        /// Returns the number of elements in a <see cref="ReadOnlySpan{T}"/>.
+        /// </summary>
+        /// <typeparam name="T">The type of elements in <paramref name="source"/>.</typeparam>
+        /// <param name="source">A <see cref="ReadOnlySpan{T}"/> whose elements are to be counted.</param>
+        /// <returns>The number of elements in <paramref name="source"/>.</returns>
+        /// <exception cref="OverflowException">The number of elements in <paramref name="source"/> is larger than <see cref="int.MaxValue"/>.</exception>
+        public static int Count<T>(this ReadOnlySpan<T> source)
+        {
+            return source.Length;
+        }
+
+        /// <summary>
+        /// Returns a number that represents how many elements in the specified sequence satisfy a condition.
+        /// </summary>
+        /// <typeparam name="T">The type of elements in <paramref name="source"/>.</typeparam>
+        /// <param name="source">A <see cref="ReadOnlySpan{T}"/> that contains elements to be tested and counted.</param>
+        /// <param name="predicate">A function to test each element for a condition.</param>
+        /// <returns>A number that represents how many elements in <paramref name="source"/> satisfy the condition in the predicate function.</returns>
+        /// <exception cref="ArgumentNullException"><paramref name="predicate"/> is null.</exception> 
+        /// <exception cref="OverflowException">The number of elements in <paramref name="source"/> is larger than <see cref="int.MaxValue"/>.</exception>
+        public static int Count<T>(this ReadOnlySpan<T> source, Predicate<T> predicate)
+        {
+            if(predicate is null)
+            {
+                throw new ArgumentNullException(nameof(predicate));
+            }
+
+            int count = 0;
+
+            foreach(var item in source)
+            {
+                checked
+                {
+                    if(predicate(item))
+                    {
+                        count++;
+                    }
+                }
+            }
+
+            return count;
+        }
+    }
+}

src/Extensions/ReadOnlySpan/Linq/Where.cs

@@ -0,0 +1,52 @@
+using System;
+using System.Collections.Generic;
+
+namespace SpanExtensions
+{
+    public static partial class ReadOnlySpanExtensions
+    {
+        /// <summary>
+        /// Filters a sequence of values based on a predicate.
+        /// </summary>
+        /// <typeparam name="T">The type of elements in <paramref name="source"/>.</typeparam>
+        /// <param name="source">The <see cref="ReadOnlySpan{T}"/> to filter.</param>
+        /// <param name="predicate">A function to test each element for a condition.</param>
+        /// <returns>A <see cref="ReadOnlySpan{T}"/> that contains elements from the input sequence that satisfy the condition.</returns>
+        /// <exception cref="ArgumentNullException"><paramref name="predicate"/> is null.</exception>
+        public static IEnumerable<T> Where<T>(this ReadOnlySpan<T> source, Predicate<T> predicate)
+        {
+            ReadOnlySpan<T>.Enumerator e = source.GetEnumerator();
+
+            while(e.MoveNext())
+            {
+                T current = e.Current;
+
+                if(predicate(current)) 
+                {
+                    yield return current;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Filters a sequence of values based on a predicate.
+        /// </summary>
+        /// <typeparam name="T">The type of elements in <paramref name="source"/>.</typeparam>
+        /// <param name="source">The <see cref="ReadOnlySpan{T}"/> to filter.</param>
+        /// <param name="predicate">A function to test each element for a condition.</param>
+        /// <returns>A <see cref="ReadOnlySpan{T}"/> that contains elements from the input sequence that satisfy the condition.</returns>
+        /// <exception cref="ArgumentNullException"><paramref name="predicate"/> is null.</exception>
+        public static IEnumerable<T> Where<T>(this ReadOnlySpan<T> source, Func<T, int, bool> predicate)
+        {
+            for(int i = 0; i < source.Length; i++)
+            {
+                T current = source[i];
+
+                if(predicate(current, i))
+                {
+                    yield return current;
+                }
+            }
+        }
+    }
+}

src/Extensions/Span/Linq/AsEnumerable.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+
+namespace SpanExtensions
+{
+    public static partial class SpanExtensions
+    {
+        /// <summary>
+        /// Returns the input typed as <see cref="IEnumerable{T}"/>.
+        /// </summary>
+        /// <param name="source">The sequence to type as <see cref="IEnumerable{T}"/>.</param>
+        /// <typeparam name="T">The type of elements in <paramref name="source"/>.</typeparam>
+        /// <returns>The input sequence typed as <see cref="IEnumerable{T}"/>.</returns>
+        public static IEnumerable<T> AsEnumerable<T>(this Span<T> source)
+        {
+            return ReadOnlySpanExtensions.AsEnumerable<T>(source);
+        }
+    }
+}

src/Extensions/Span/Linq/Count.cs

@@ -0,0 +1,33 @@
+using System;
+
+namespace SpanExtensions
+{
+    public static partial class SpanExtensions
+    {
+        /// <summary>
+        /// Returns the number of elements in a <see cref="Span{T}"/>.
+        /// </summary>
+        /// <typeparam name="T">The type of elements in <paramref name="source"/>.</typeparam>
+        /// <param name="source">A <see cref="Span{T}"/> whose elements are to be counted.</param>
+        /// <returns>The number of elements in <paramref name="source"/>.</returns>
+        /// <exception cref="OverflowException">The number of elements in <paramref name="source"/> is larger than <see cref="int.MaxValue"/>.</exception>
+        public static int Count<T>(this Span<T> source)
+        {
+            return ReadOnlySpanExtensions.Count<T>(source);
+        }
+
+        /// <summary>
+        /// Returns a number that represents how many elements in the specified sequence satisfy a condition.
+        /// </summary>
+        /// <typeparam name="T">The type of elements in <paramref name="source"/>.</typeparam>
+        /// <param name="source">A <see cref="Span{T}"/> that contains elements to be tested and counted.</param>
+        /// <param name="predicate">A function to test each element for a condition.</param>
+        /// <returns>A number that represents how many elements in <paramref name="source"/> satisfy the condition in the predicate function.</returns>
+        /// <exception cref="ArgumentNullException"><paramref name="predicate"/> is null.</exception> 
+        /// <exception cref="OverflowException">The number of elements in <paramref name="source"/> is larger than <see cref="int.MaxValue"/>.</exception>
+        public static int Count<T>(this Span<T> source, Predicate<T> predicate)
+        {
+            return ReadOnlySpanExtensions.Count(source, predicate);
+        }
+    }
+}

src/Extensions/Span/Linq/SingleOrDefault.cs

@@ -39,7 +39,7 @@ public static T SingleOrDefault<T>(this Span<T> source, Predicate<T> predicate,
         /// <returns>The single element in <paramref name="source"/>.</returns>
         public static T? SingleOrDefault<T>(this Span<T> source)
         {
-            return ReadOnlySpanExtensions.SingleOrDefault<T>(source);    
+            return ReadOnlySpanExtensions.SingleOrDefault<T>(source);
         }
 
         /// <summary>

src/Extensions/Span/Linq/Where.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Collections.Generic;
+
+namespace SpanExtensions
+{
+    public static partial class SpanExtensions
+    {
+        /// <summary>
+        /// Filters a sequence of values based on a predicate.
+        /// </summary>
+        /// <typeparam name="T">The type of elements in <paramref name="source"/>.</typeparam>
+        /// <param name="source">The <see cref="Span{T}"/> to filter.</param>
+        /// <param name="predicate">A function to test each element for a condition.</param>
+        /// <returns>A <see cref="Span{T}"/> that contains elements from the input sequence that satisfy the condition.</returns>
+        /// <exception cref="ArgumentNullException"><paramref name="predicate"/> is null.</exception>
+        public static IEnumerable<T> Where<T>(this Span<T> source, Predicate<T> predicate)
+        {
+            return ReadOnlySpanExtensions.Where(source, predicate);
+        }
+
+        /// <summary>
+        /// Filters a sequence of values based on a predicate.
+        /// </summary>
+        /// <typeparam name="T">The type of elements in <paramref name="source"/>.</typeparam>
+        /// <param name="source">The <see cref="Span{T}"/> to filter.</param>
+        /// <param name="predicate">A function to test each element for a condition.</param>
+        /// <returns>A <see cref="Span{T}"/> that contains elements from the input sequence that satisfy the condition.</returns>
+        /// <exception cref="ArgumentNullException"><paramref name="predicate"/> is null.</exception>
+        public static IEnumerable<T> Where<T>(this Span<T> source, Func<T, int, bool> predicate)
+        {
+            return ReadOnlySpanExtensions.Where(source, predicate);
+        }
+    }
+}