Under annotations

CSharpMath.Core.Tests/Atom/LaTeXParserTest.cs

@@ -408,6 +408,34 @@ public void TestUnderline() {
       Assert.Equal(@"\underline{2}", LaTeXParser.MathListToLaTeX(list).ToString());
     }
 
+    /// <summary>
+    /// Test underbrace without under
+    /// </summary>
+    [Fact]
+    public void TestUnderbrace() {
+      var list = ParseLaTeX(@"\underbrace{x}");
+
+      Assert.Collection(list,
+        CheckAtom<UnderAnnotation>("\u23df", underBrace =>
+          Assert.Collection(underBrace.InnerList, CheckAtom<Variable>("x"))
+        )
+      );
+    }
+
+    /// <summary>
+    /// Test underbrace with under (not implemented yet)
+    /// </summary>
+    // [Fact]
+    // public void TestUnderbraceWithUnder() {
+    //   var list = ParseLaTeX(@"\underbrace{x}_{y}");
+
+    //   Assert.Collection(list,
+    //     CheckAtom<UnderAnnotation>("\u23df", underBrace =>
+    //       Assert.Collection(underBrace.InnerList, CheckAtom<Variable>("x"))
+    //     )
+    //   );
+    // }
+
     [Fact]
     public void TestAccent() {
       var list = ParseLaTeX(@"\bar x");

CSharpMath/Atom/Atoms/UnderAnnotation.cs

@@ -0,0 +1,30 @@
+namespace CSharpMath.Atom.Atoms; 
+/// <summary>
+/// Abstract name of under annotations implementation \underbrace, \underbracket etc..
+/// </summary>
+public sealed class UnderAnnotation : MathAtom, IMathListContainer {
+  public UnderAnnotation(string value, MathList innerList, MathList? underList = null) : base(value) {
+    InnerList = innerList;
+    UnderList = underList;
+  }
+
+  public MathList InnerList { get; }
+  public MathList? UnderList { get; }
+
+  System.Collections.Generic.IEnumerable<MathList> IMathListContainer.InnerLists =>
+    new[] { InnerList };
+  public new UnderAnnotation Clone(bool finalize) => (UnderAnnotation)base.Clone(finalize);
+  protected override MathAtom CloneInside(bool finalize) =>
+    new UnderAnnotation(Nucleus, InnerList.Clone(finalize), UnderList?.Clone(finalize));
+  public override bool ScriptsAllowed => true;
+  //depending on nucleus, DebugString will change to \underbrace , \underbracket etc..
+  public override string DebugString =>
+    new System.Text.StringBuilder(@"\underbrace")
+    .AppendInBracesOrLiteralNull(InnerList.DebugString)
+    .ToString();
+  public bool EqualsUnderAnnotation(UnderAnnotation other) =>
+    EqualsAtom(other) && InnerList.EqualsList(other.InnerList);
+  public override bool Equals(object obj) =>
+    obj is UnderAnnotation u ? EqualsUnderAnnotation(u) : false;
+  public override int GetHashCode() => (base.GetHashCode(), InnerList).GetHashCode();
+}

CSharpMath/Atom/LaTeXParser.cs

@@ -618,6 +618,14 @@ static bool MathAtomToLaTeX(MathAtom atom, StringBuilder builder,
             builder.Append(@"\underline{");
             MathListToLaTeX(under.InnerList, builder, currentFontStyle);
             builder.Append('}');
+            break;
+          case UnderAnnotation underAnotation:
+            if (MathAtomToLaTeX(underAnotation, builder, out var underAnnotationCommand)) {
+              builder.Append(@$"\{underAnnotationCommand}{{");
+              MathListToLaTeX(underAnotation.InnerList, builder, currentFontStyle);
+              builder.Append('}');
+            }
+
             break;
           case Accent accent:
             MathAtomToLaTeX(accent, builder, out _);

CSharpMath/Atom/LaTeXSettings.cs

@@ -160,6 +160,9 @@ public static class LaTeXSettings {
           parser.ReadArgument().Bind(mathList => Ok(new Overline(mathList))) },
         { @"\underline", (parser, accumulate, stopChar) =>
           parser.ReadArgument().Bind(mathList => Ok(new Underline(mathList))) },
+        { @"\underbrace", (parser, accumulate, stopChar) => 
+          parser.ReadArgument().Bind(mathList => Ok(new UnderAnnotation("\u23df", mathList)))},
+          //Adding under element should happen when adding sub script later or here?
         { @"\begin", (parser, accumulate, stopChar) =>
           parser.ReadEnvironment().Bind(env =>
             parser.ReadTable(env, null, false, stopChar)).Bind(Ok) },