Can now use Category for specifying what most of the lambda checkers …

…were used for.

Stringier.Patterns/CategoryChecker.cs

@@ -0,0 +1,65 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using System.Traits;
+
+namespace Stringier.Patterns {
+	internal sealed class CategoryChecker : Checker {
+		/// <summary>
+		/// The category to match.
+		/// </summary>
+		[DisallowNull, NotNull]
+		private readonly Category Category;
+
+		/// <summary>
+		/// Initializes a new <see cref="CategoryChecker"/>.
+		/// </summary>
+		/// <param name="category">The category to match.</param>
+		public CategoryChecker([DisallowNull] Category category) => Category = category;
+
+		/// <inheritdoc/>
+		protected internal override void Consume(ReadOnlyMemory<Char> source, ref Int32 location, [AllowNull, MaybeNull] out Exception exception, [AllowNull] IAdd<Capture> trace) => Consume(source.Span, ref location, out exception, trace);
+
+		/// <inheritdoc/>
+		protected internal override unsafe void Consume([DisallowNull] Char* source, Int32 length, ref Int32 location, [AllowNull, MaybeNull] out Exception exception, [AllowNull] IAdd<Capture> trace) => Consume(new ReadOnlySpan<Char>(source, length), ref location, out exception, trace);
+
+		/// <inheritdoc/>
+		protected internal override Boolean IsConsumeHeader(ReadOnlySpan<Char> source, Int32 location) => Category.Contains(source[location]);
+
+		/// <inheritdoc/>
+		protected internal override Boolean IsNeglectHeader(ReadOnlySpan<Char> source, Int32 location) => !Category.Contains(source[location]);
+
+		/// <inheritdoc/>
+		protected internal override void Neglect(ReadOnlyMemory<Char> source, ref Int32 location, [AllowNull, MaybeNull] out Exception exception, [AllowNull] IAdd<Capture> trace) => Neglect(source.Span, ref location, out exception, trace);
+
+		/// <inheritdoc/>
+		protected internal override unsafe void Neglect([DisallowNull] Char* source, Int32 length, ref Int32 location, [AllowNull, MaybeNull] out Exception exception, [AllowNull] IAdd<Capture> trace) => Neglect(new ReadOnlySpan<Char>(source, length), ref location, out exception, trace);
+
+		private void Consume(ReadOnlySpan<Char> source, ref Int32 location, [AllowNull, MaybeNull] out Exception exception, [AllowNull] IAdd<Capture> trace) {
+			if (location == source.Length) {
+				exception = AtEnd;
+				trace?.Add(exception, location);
+			} else if (Category.Contains(source[location])) {
+				trace?.Add(source[location], location);
+				location++;
+				exception = null;
+			} else {
+				exception = NoMatch;
+				trace?.Add(exception, location);
+			}
+		}
+
+		private void Neglect(ReadOnlySpan<Char> source, ref Int32 location, [AllowNull, MaybeNull] out Exception exception, [AllowNull] IAdd<Capture> trace) {
+			if (location == source.Length) {
+				exception = AtEnd;
+				trace?.Add(exception, location);
+			} else if (!Category.Contains(source[location])) {
+				trace?.Add(source[location], location);
+				location++;
+				exception = null;
+			} else {
+				exception = NoMatch;
+				trace?.Add(exception, location);
+			}
+		}
+	}
+}

Stringier.Patterns/Pattern.cs

@@ -8,21 +8,6 @@ namespace Stringier.Patterns {
 	/// Represents a textual pattern.
 	/// </summary>
 	public abstract partial class Pattern {
-		/// <summary>
-		/// Check for the end of the line.
-		/// </summary>
-		/// <remarks>
-		/// This checks for various OS line endings, properly handling Windows convention, not just single UNICODE line terminators.
-		/// </remarks>
-		[NotNull, DisallowNull]
-		public static readonly Pattern EndOfLine = new LineEndChecker();
-
-		/// <summary>
-		/// Check for the end of the source.
-		/// </summary>
-		[NotNull, DisallowNull]
-		public static readonly Pattern EndOfSource = new SourceEndChecker();
-
 		/// <summary>
 		/// Predefined <see cref="Exception"/> for when the end of the source was reached before finding a match.
 		/// </summary>
@@ -32,11 +17,27 @@ public abstract partial class Pattern {
 		/// Predefined <see cref="Exception"/> for when no match could be found.
 		/// </summary>
 		protected static readonly Exception NoMatch = new InvalidOperationException("The parser failed to find a match for the pattern in the source.");
+
 		/// <summary>
 		/// Initialize a new <see cref="Pattern"/>.
 		/// </summary>
 		protected Pattern() { }
 
+		/// <summary>
+		/// Check for the end of the line.
+		/// </summary>
+		/// <remarks>
+		/// This checks for various OS line endings, properly handling Windows convention, not just single UNICODE line terminators.
+		/// </remarks>
+		[NotNull, DisallowNull]
+		public static Pattern EndOfLine { get; } = new LineEndChecker();
+
+		/// <summary>
+		/// Check for the end of the source.
+		/// </summary>
+		[NotNull, DisallowNull]
+		public static Pattern EndOfSource { get; } = new SourceEndChecker();
+
 		#region Conversions
 		/// <summary>
 		/// Converts to a <see cref="Pattern"/> matching exactly the <paramref name="char"/>.
@@ -135,6 +136,13 @@ protected Pattern() { }
 		/// <param name="capture">A <see cref="ValueTuple{T1, T2}"/> of <see cref="Patterns.Capture"/> to match and <see cref="Case"/> comparison.</param>
 		[return: NotNull]
 		public static implicit operator Pattern((Capture, Case) capture) => new CaptureLiteral(capture.Item1, capture.Item2);
+
+		/// <summary>
+		/// Converts to a <see cref="Pattern"/> matching exactly the <paramref name="category"/>.
+		/// </summary>
+		/// <param name="category">The <see cref="Category"/> to match.</param>
+		[return: MaybeNull, NotNullIfNotNull("category")]
+		public static implicit operator Pattern([AllowNull] Category category) => category is not null ? new CategoryChecker(category) : null;
 		#endregion
 
 		#region Parse(Source, ref Int32)

Tests.CSharp/Pattern_Tests.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Text;
+using Stringier;
 using Stringier.Patterns;
 using static Stringier.Patterns.Pattern;
 using Xunit;
@@ -38,6 +39,41 @@ public void Alternator_String(String expected, String first, String second, Stri
 			Assert.Equal(expected.Length, i);
 		}
 
+		[Theory]
+		[InlineData("A", "A")]
+		[InlineData("A", "Abc")]
+		[InlineData("A", "ABC")]
+		public unsafe void CategoryChecker_Pointer(String expected, String source) {
+			Pattern ptn = Category.UppercaseLetter;
+			Int32 i = 0;
+			Capture? capture = null;
+			fixed (Char* src = source) {
+				capture = ptn.Parse(source, ref i);
+				Assert.Equal(expected, capture);
+			}
+			Assert.Equal(expected.Length, i);
+		}
+
+		[Theory]
+		[InlineData("A", "A", false)]
+		[InlineData("A", "Abc", false)]
+		[InlineData("A", "ABC", false)]
+		[InlineData("", "a", true)]
+		[InlineData("", "abc", true)]
+		public void CategoryChecker_String(String expected, String source, Boolean throws) {
+			Pattern ptn = Category.UppercaseLetter;
+			Int32 i = 0;
+			Capture? capture = null;
+			if (!throws) {
+				capture = ptn.Parse(source, ref i);
+				Assert.Equal(expected, capture);
+			} else {
+				_ = Assert.ThrowsAny<Exception>(() => capture = ptn.Parse(source, ref i));
+				Assert.Null(capture);
+			}
+			Assert.Equal(expected.Length, i);
+		}
+
 		[Theory]
 		[InlineData("one", "one", "two", "three", "one")]
 		[InlineData("two", "one", "two", "three", "two")]

docs/api/Stringier.Patterns.Bias.html

@@ -73,7 +73,7 @@
 
   <h1 id="Stringier_Patterns_Bias" data-uid="Stringier.Patterns.Bias" class="text-break">Enum Bias
   </h1>
-  <div class="markdown level0 summary"><p>Word letter bias, used by <span class="xref">Stringier.Patterns.WordChecker</span>.</p>
+  <div class="markdown level0 summary"><p>Word letter bias, used by <see cref="!:WordChecker"></see>.</p>
 </div>
   <div class="markdown level0 conceptual"></div>
   <h6><strong>Namespace</strong>: <a class="xref" href="Stringier.Patterns.html">Stringier.Patterns</a></h6>