From e07f175b448143b11c61ce0ebe84c42a6e21b727 Mon Sep 17 00:00:00 2001
From: Hadrian Tang <hadrianwttang@outlook.com>
Date: Mon, 31 Aug 2026 06:13:09 +0800
Subject: [PATCH] feat: support rising diagonal ellipsis

---
 CSharpMath.Core.Tests/Atom/LaTeXParserTest.cs | 17 +++++++++++++++++
 CSharpMath/Atom/LaTeXSettings.cs              |  3 ++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/CSharpMath.Core.Tests/Atom/LaTeXParserTest.cs b/CSharpMath.Core.Tests/Atom/LaTeXParserTest.cs
index 9d122367..cf2b8ee7 100644
--- a/CSharpMath.Core.Tests/Atom/LaTeXParserTest.cs
+++ b/CSharpMath.Core.Tests/Atom/LaTeXParserTest.cs
@@ -52,6 +52,7 @@ public static Action<MathAtom> CheckAtom<T>
     [InlineData(@"\pi+\theta\geq 3", new[] { typeof(Variable), typeof(BinaryOperator), typeof(Variable), typeof(Relation), typeof(Number) }, @"\pi +\theta \geq 3")]
     // aliases
     [InlineData(@"\pi\ne 5 \land 3", new[] { typeof(Variable), typeof(Relation), typeof(Number), typeof(BinaryOperator), typeof(Number) }, @"\pi \neq 5\wedge 3")]
+    [InlineData(@"\udots", new[] { typeof(Ordinary) }, @"\udots ")]
     // control space
     [InlineData(@"x \ y", new[] { typeof(Variable), typeof(Ordinary), typeof(Variable) }, @"x\  y")]
     // spacing
@@ -96,6 +97,22 @@ public void ControlWordDoesNotConsumeFollowingStar() {
       Assert.Equal(@"\sin *", LaTeXParser.MathListToLaTeX(list).ToString());
     }
 
+    [Fact]
+    public void TestUdotsPreservesOrdinaryNucleusInScriptsAndTables() {
+      var direct = Assert.IsType<Ordinary>(ParseLaTeX(@"\udots").Atoms[0]);
+      Assert.Equal("\u22F0", direct.Nucleus);
+      Assert.Equal(@"\udots ", LaTeXParser.MathListToLaTeX(new MathList(direct)).ToString());
+
+      var scripted = Assert.IsType<Ordinary>(ParseLaTeX(@"\udots^a_b").Atoms[0]);
+      Assert.Equal("\u22F0", scripted.Nucleus);
+      Assert.NotNull(scripted.Superscript);
+      Assert.NotNull(scripted.Subscript);
+
+      var matrix = Assert.IsType<Table>(ParseLaTeX(@"\begin{matrix}\udots&x\\y&\udots\end{matrix}").Atoms[0]);
+      Assert.Equal("\u22F0", matrix.Cells[0][0].Atoms.OfType<Ordinary>().Single().Nucleus);
+      Assert.Equal("\u22F0", matrix.Cells[1][1].Atoms.OfType<Ordinary>().Single().Nucleus);
+    }
+
     /// new[] { Base list }, new[] { Script of first atom }, new[] { Script of first atom inside script of first atom }
     [Theory]
     [InlineData("x^2", "x^2", new[] { typeof(Variable) }, new[] { typeof(Number) })]
diff --git a/CSharpMath/Atom/LaTeXSettings.cs b/CSharpMath/Atom/LaTeXSettings.cs
index 3ef5599a..db86e8e8 100644
--- a/CSharpMath/Atom/LaTeXSettings.cs
+++ b/CSharpMath/Atom/LaTeXSettings.cs
@@ -591,6 +591,7 @@ atom is Accent accent
         { @"\dag", new Ordinary("†") },
         { @"\ddag", new Ordinary("‡") },
         { @"\dots", new Ordinary("…") },
+        { @"\udots", new Ordinary("⋰") },
         { @"\pounds", new Ordinary("£") },
         // \{ is defined in Table 1
         // \} is defined in Table 1
@@ -1189,4 +1190,4 @@ atom is Accent accent
         // \varsupsetneqq -> ⫌ + U+FE00 (Variation Selector 1) Not dealing with variation selectors, thank you very much
       };
   }
-}
\ No newline at end of file
+}