Add generic version of "Sequence" for any number type

This is a squashed merge of PR #893 that closes #892.

MoreLinq.Test/NullArgumentTest.cs

@@ -92,20 +92,19 @@ static MethodInfo InstantiateMethod(MethodInfo definition)
         {
             if (!definition.IsGenericMethodDefinition) return definition;
 
-            var typeArguments = definition.GetGenericArguments().Select(t => InstantiateType(t.GetTypeInfo())).ToArray();
-            return definition.MakeGenericMethod(typeArguments);
-        }
-
-        static Type InstantiateType(TypeInfo typeParameter)
-        {
-            var constraints = typeParameter.GetGenericParameterConstraints();
-
-            return constraints.Length switch
-            {
-                0 => typeof(int),
-                1 => constraints.Single(),
-                _ => throw new NotImplementedException("NullArgumentTest.InstantiateType")
-            };
+            var typeArguments =
+                from t in definition.GetGenericArguments()
+                select t.GetGenericParameterConstraints() switch
+                {
+                    { Length: 0 } => typeof(int),
+#if NET7_0_OR_GREATER
+                    var constraints when constraints.Any(t => t.IsGenericType && t.GetGenericTypeDefinition() == typeof(System.Numerics.INumber<>)) => typeof(int),
+#endif
+                    { Length: 1 } constraints => constraints.Single(),
+                    _ => throw new NotImplementedException("NullArgumentTest.InstantiateType")
+                };
+
+            return definition.MakeGenericMethod(typeArguments.ToArray());
         }
 
         static bool IsReferenceType(ParameterInfo parameter) =>

MoreLinq/MoreLinq.csproj

@@ -213,8 +213,12 @@
     <DefineConstants>$(DefineConstants);MORELINQ</DefineConstants>
   </PropertyGroup>
 
+  <PropertyGroup Condition="'$(TargetFramework)' == 'netstandard2.1' Or '$(TargetFramework)' == 'net6.0' ">
+    <DefineConstants>$(DefineConstants);NO_STATIC_ABSTRACTS</DefineConstants>
+  </PropertyGroup>
+
   <PropertyGroup Condition="'$(TargetFramework)' == 'netstandard2.0'">
-    <DefineConstants>$(DefineConstants);NO_ASYNC_STREAMS;NO_BUFFERS</DefineConstants>
+    <DefineConstants>$(DefineConstants);NO_STATIC_ABSTRACTS;NO_ASYNC_STREAMS;NO_BUFFERS</DefineConstants>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(TargetFramework)' != 'netstandard2.0' And '$(TargetFramework)' != 'net6.0'">

MoreLinq/PublicAPI/net8.0/PublicAPI.Unshipped.txt

@@ -1 +1,4 @@
 #nullable enable
+static MoreLinq.MoreEnumerable.Sequence<T>(T start) -> System.Collections.Generic.IEnumerable<T>!
+static MoreLinq.MoreEnumerable.Sequence<T>(T start, T stop) -> System.Collections.Generic.IEnumerable<T>!
+static MoreLinq.MoreEnumerable.Sequence<T>(T start, T stop, T step) -> System.Collections.Generic.IEnumerable<T>!

MoreLinq/Sequence.cs

@@ -15,6 +15,90 @@
 // limitations under the License.
 #endregion
 
+#if !NO_STATIC_ABSTRACTS
+
+namespace MoreLinq
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Numerics;
+
+    static partial class MoreEnumerable
+    {
+        /// <summary>
+        /// Generates a sequence of numbers starting with the given value and in steps of 1.
+        /// </summary>
+        /// <typeparam name="T">
+        /// A type that represents a number and defines its minimum and maximum representable value.
+        /// </typeparam>
+        /// <param name="start">The value of the first number in the sequence.</param>
+        /// <returns>
+        /// A sequence of sequential numbers starting with <paramref name="start"/> and up to the
+        /// maximum representable value, in increments of 1.</returns>
+        /// <remarks>
+        /// This operator uses deferred execution and streams its results.
+        /// </remarks>
+
+        public static IEnumerable<T> Sequence<T>(T start)
+            where T : INumber<T>, IMinMaxValue<T> =>
+            Sequence(start, T.MaxValue, T.One);
+
+        /// <summary>
+        /// Generates a sequence of numbers within the (inclusive) specified range.
+        /// If sequence is ascending the step is +1, otherwise -1.
+        /// </summary>
+        /// <typeparam name="T">A type that represents a number.</typeparam>
+        /// <param name="start">The value of the first number in the sequence.</param>
+        /// <param name="stop">The value of the last number in the sequence.</param>
+        /// <returns>A sequence of sequential numbers.</returns>
+        /// <remarks>
+        /// This operator uses deferred execution and streams its results.
+        /// </remarks>
+
+        public static IEnumerable<T> Sequence<T>(T start, T stop)
+            where T : INumber<T> =>
+            Sequence(start, stop, stop < start ? -T.One : T.One);
+
+        /// <summary>
+        /// Generates a sequence of numbers within the (inclusive) specified range. An additional
+        /// parameter specifies the steps in which the numbers of the sequence increase or decrease.
+        /// </summary>
+        /// <typeparam name="T">A type that represents a number.</typeparam>
+        /// <param name="start">The value of the first number in the sequence.</param>
+        /// <param name="stop">The value of the last number in the sequence.</param>
+        /// <param name="step">The step to define the next number.</param>
+        /// <returns>A sequence of sequential numbers.</returns>
+        /// <remarks>
+        /// <para>
+        /// This operator uses deferred execution and streams its results.</para>
+        /// <para>
+        /// When <paramref name="step"/> is equal to zero, this operator returns an infinite
+        /// sequence where all elements are equal to <paramref name="start"/>.</para>
+        /// </remarks>
+
+        public static IEnumerable<T> Sequence<T>(T start, T stop, T step)
+            where T : INumber<T>
+        {
+            var current = start;
+
+            while (step >= T.Zero ? stop >= current : stop <= current)
+            {
+                yield return current;
+                try
+                {
+                    current = checked(current + step);
+                }
+                catch (OverflowException)
+                {
+                    yield break;
+                }
+            }
+        }
+    }
+}
+
+#endif // !NO_STATIC_ABSTRACTS
+
 namespace MoreLinq
 {
     using System.Collections.Generic;
@@ -38,10 +122,12 @@ static partial class MoreEnumerable
         /// The <c>result</c> variable will contain <c>{ 6, 5, 4, 3, 2, 1, 0 }</c>.
         /// </example>
 
-        public static IEnumerable<int> Sequence(int start, int stop)
-        {
-            return Sequence(start, stop, start < stop ? 1 : -1);
-        }
+        public static IEnumerable<int> Sequence(int start, int stop) =>
+#if !NO_STATIC_ABSTRACTS
+            Sequence<int>(start, stop);
+#else
+            Sequence(start, stop, start < stop ? 1 : -1);
+#endif
 
         /// <summary>
         /// Generates a sequence of integral numbers within the (inclusive) specified range.
@@ -53,7 +139,7 @@ public static IEnumerable<int> Sequence(int start, int stop)
         /// <returns>An <see cref="IEnumerable{Int32}"/> that contains a range of sequential integral numbers.</returns>
         /// <remarks>
         /// When <paramref name="step"/> is equal to zero, this operator returns an
-        /// infinite sequence where all elements are equals to <paramref name="start"/>.
+        /// infinite sequence where all elements are equal to <paramref name="start"/>.
         /// This operator uses deferred execution and streams its results.
         /// </remarks>
         /// <example>
@@ -65,6 +151,9 @@ public static IEnumerable<int> Sequence(int start, int stop)
 
         public static IEnumerable<int> Sequence(int start, int stop, int step)
         {
+#if !NO_STATIC_ABSTRACTS
+            return Sequence<int>(start, stop, step);
+#else
             long current = start;
 
             while (step >= 0 ? stop >= current
@@ -73,6 +162,7 @@ public static IEnumerable<int> Sequence(int start, int stop, int step)
                 yield return (int)current;
                 current += step;
             }
+#endif
         }
     }
 }