Merge pull request #12 from Orace/vto-Lead

Lead overload returning tuple (T, T).

MoreLinq/Extensions.g.cs

@@ -3247,6 +3247,37 @@ public static T LastOrDefault<T>(this IExtremaEnumerable<T> source)
     [GeneratedCode("MoreLinq.ExtensionsGenerator", "1.0.0.0")]
     public static partial class LeadExtension
     {
+
+        /// <summary>
+        /// Produces a sequence of tuple containing a pair of elements separated by a positive offset.
+        /// </summary>
+        /// <remarks>
+        /// This operator evaluates in a deferred and streaming manner.<br/>
+        /// For elements of the sequence that are less than <paramref name="offset"/> items from the end,
+        /// default(T) is used as the lead value.<br/>
+        /// </remarks>
+        /// <typeparam name="TSource">The type of the elements in the source sequence</typeparam>
+        /// <param name="source">The sequence over which to evaluate Lead</param>
+        /// <param name="offset">The offset (expressed as a positive number) by which to lead each element of the sequence</param>
+        /// <returns>The produced sequence of tuple</returns>
+
+        public static IEnumerable<(TSource Item, TSource OffsetItem)> Lead<TSource>(this IEnumerable<TSource> source, int offset)
+            => MoreEnumerable.Lead(source, offset);
+
+        /// <summary>
+        /// Produces a sequence of tuple containing a pair of elements separated by a positive offset.
+        /// </summary>
+        /// <remarks>
+        /// This operator evaluates in a deferred and streaming manner.<br/>
+        /// </remarks>
+        /// <typeparam name="TSource">The type of the elements in the source sequence</typeparam>
+        /// <param name="source">The sequence over which to evaluate Lead</param>
+        /// <param name="offset">The offset (expressed as a positive number) by which to lead each element of the sequence</param>
+        /// <param name="defaultLeadValue">A default value supplied for the leading element when none is available</param>
+        /// <returns>The produced sequence of tuple</returns>
+
+        public static IEnumerable<(TSource Item, TSource OffsetItem)> Lead<TSource>(this IEnumerable<TSource> source, int offset, TSource defaultLeadValue)
+            => MoreEnumerable.Lead(source, offset, defaultLeadValue);
         /// <summary>
         /// Produces a projection of a sequence by evaluating pairs of elements separated by a positive offset.
         /// </summary>

MoreLinq/Lead.cs

@@ -85,5 +85,40 @@ public static IEnumerable<TResult> Lead<TSource, TResult>(this IEnumerable<TSour
                     yield return resultSelector(leadQueue.Dequeue(), defaultLeadValue);
             }
         }
+
+        /// <summary>
+        /// Produces a sequence of tuple containing a pair of elements separated by a positive offset.
+        /// </summary>
+        /// <remarks>
+        /// This operator evaluates in a deferred and streaming manner.<br/>
+        /// For elements of the sequence that are less than <paramref name="offset"/> items from the end,
+        /// default(T) is used as the lead value.<br/>
+        /// </remarks>
+        /// <typeparam name="TSource">The type of the elements in the source sequence</typeparam>
+        /// <param name="source">The sequence over which to evaluate Lead</param>
+        /// <param name="offset">The offset (expressed as a positive number) by which to lead each element of the sequence</param>
+        /// <returns>The produced sequence of tuple</returns>
+
+        public static IEnumerable<(TSource Item, TSource OffsetItem)> Lead<TSource>(this IEnumerable<TSource> source, int offset)
+        {
+            return Lead(source, offset, default, ValueTuple.Create);
+        }
+
+        /// <summary>
+        /// Produces a sequence of tuple containing a pair of elements separated by a positive offset.
+        /// </summary>
+        /// <remarks>
+        /// This operator evaluates in a deferred and streaming manner.<br/>
+        /// </remarks>
+        /// <typeparam name="TSource">The type of the elements in the source sequence</typeparam>
+        /// <param name="source">The sequence over which to evaluate Lead</param>
+        /// <param name="offset">The offset (expressed as a positive number) by which to lead each element of the sequence</param>
+        /// <param name="defaultLeadValue">A default value supplied for the leading element when none is available</param>
+        /// <returns>The produced sequence of tuple</returns>
+
+        public static IEnumerable<(TSource Item, TSource OffsetItem)> Lead<TSource>(this IEnumerable<TSource> source, int offset, TSource defaultLeadValue)
+        {
+            return Lead(source, offset, default, ValueTuple.Create);
+        }
     }
 }

README.md

@@ -358,7 +358,7 @@ This method has 4 overloads.
 Produces a projection of a sequence by evaluating pairs of elements separated
 by a positive offset.
 
-This method has 2 overloads.
+This method has 4 overloads.
 
 ### LeftJoin