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LaTeX reader: a script in brackets that close, x^(a+b), as one group #35

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Merged
simonebortolin merged 1 commit into from
Nov 11, 2026
+27 −16
Merged

LaTeX reader: a script in brackets that close, x^(a+b), as one group #35

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37 changes: 22 additions & 15 deletions src/SharpEquations/Internal/LaTeX/LaTeXReader.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1281,15 +1281,17 @@ void Close((int Open, List<int> Bars) frame, bool inBrackets, int close)

/// <summary>
/// A bracket that a group opens and does not close, as in \phantom{(}, escaped: UnicodeMath would close it with an
/// empty fence at the end of the group; so are a closing bracket alone in a group (x^{)}) and a bracket
/// that is a script and does not close (x_(). The text of \text and the like is left as it is.
/// empty fence at the end of the group; so are a closing bracket alone in a group (x^{)}) and a bracket that is a
/// script and does not close (x_(). A script in brackets that close is grouped whole (x^(a+b) as x^{(a+b)}). The
/// text of \text and the like is left as it is.
/// </summary>
private static string EscapeOpenBrackets(string latex)
{
var tex = new Text(latex);
var groups = new Stack<List<int>>();
var escaped = new List<int>();
var scripts = new HashSet<int>();
// the scripts grouped, from the index of their first character to that of their last
var scripts = new Dictionary<int, int>();
for (int i = 0; i < tex.Length; i++)
{
switch (tex[i])
Expand Down Expand Up @@ -1330,27 +1332,32 @@ private static string EscapeOpenBrackets(string latex)
break;
case "_" or "^":
{
// a bracket that is a script and closes nothing, x^), or opens what does not close, x_(: Word's LaTeX
// groups a script in brackets (x^(a+b)), which UnicodeMath would read as the opening of what follows
// a bracket that is a script and closes nothing, x^), or opens what does not close, x_(, which
// UnicodeMath would read as the opening of what follows; a script in brackets that close, x^(a+b),
// is grouped whole, as Word's LaTeX writes it and Word reads it (x^{(a+b)})
int k = i + 1;
while (tex[k] == " ")
k++;
if (tex[k] is ")" or "]" || tex[k] is "(" or "[" && !BracketCloses(tex, k))
var close = tex[k] is "(" or "[" ? ClosingBracket(tex, k) : -1;
if (close >= 0)
scripts[k] = close;
else if (tex[k] is "(" or "[" or ")" or "]")
{
escaped.Add(k);
scripts.Add(k);
scripts[k] = k;
i = k;
}
break;
}
}
}
if (escaped.Count == 0)
if (escaped.Count == 0 && scripts.Count == 0)
return latex;
var ends = scripts.Values.ToList();
var result = new StringBuilder();
for (int i = 0; i < tex.Length; i++)
{
if (scripts.Contains(i))
if (scripts.ContainsKey(i))
result.Append('{');
if (escaped.Contains(i))
{
Expand All @@ -1364,7 +1371,7 @@ private static string EscapeOpenBrackets(string latex)
}
else
result.Append(tex[i]);
if (scripts.Contains(i))
foreach (var _ in ends.Where(end => end == i))
result.Append('}');
}
return result.ToString();
Expand All @@ -1379,8 +1386,8 @@ private static string Blank(Text tex, int i, int step)
return i >= 0 && i < tex.Length ? tex[i] : null;
}

/// <summary>Whether the bracket at the index closes before the group around it ends.</summary>
private static bool BracketCloses(Text tex, int open)
/// <summary>The index of the bracket that closes the one at the index before the group around it ends; -1 if none.</summary>
private static int ClosingBracket(Text tex, int open)
{
int depth = 0, braces = 0;
for (int i = open; i < tex.Length; i++)
Expand All @@ -1394,18 +1401,18 @@ private static bool BracketCloses(Text tex, int open)
braces++;
break;
case "}" when braces == 0:
return false;
return -1;
case "}":
braces--;
break;
case "(" or "[":
depth++;
break;
case ")" or "]" when --depth == 0:
return true;
return i;
}
}
return false;
return -1;
}

/// <summary>The count arguments (braced or single characters) at the index, and the index after them; null if missing.</summary>
Expand Down
6 changes: 5 additions & 1 deletion tests/SharpEquations.Tests/LaTeX/LaTeXReaderTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -172,7 +172,7 @@ public async Task ReadsLessCommonCommands(string latex, string expectedLaTeX, st

// a slash and a bar are ordinary characters of LaTeX, which UnicodeMath reads as a fraction and an absolute value;
// so is a bracket that a group opens and does not close, which UnicodeMath would close, or a bracket alone as a
// script; a bar in text, after \bigm (a relation) or {|} is a bar alone, which no other bar pairs with
// script (a script in brackets that close is grouped whole, x^(a+b), as Word reads it); a bar in text, after \bigm (a relation) or {|} is a bar alone, which no other bar pairs with
[Test]
[Arguments(@"a/b", @"a/b", @"𝑎\/𝑏")]
[Arguments(@"(a+b)/2", @"(a+b)/2", @"(𝑎+𝑏)\/2")]
Expand All @@ -199,6 +199,10 @@ public async Task ReadsLessCommonCommands(string latex, string expectedLaTeX, st
[Arguments(@"x_(", @"x_{(}", @"𝑥_\(")]
[Arguments(@"x^{)}", @"x^{)}", @"𝑥^\)")]
[Arguments(@"x^{ ] }", @"x^{]}", @"𝑥^\]")]
[Arguments(@"x^(a+b)", @"x^{(a+b)}", @"𝑥^((𝑎+𝑏))")]
[Arguments(@"x_[i]y", @"x_{[i]}y", @"𝑥_[𝑖] 𝑦")]
[Arguments(@"x^ (a)(b)", @"x^{(a)}(b)", @"𝑥^((𝑎)) (𝑏)")]
[Arguments(@"e^(i\pi)_n", @"e_n^{(i\pi)}", @"𝑒_𝑛^((𝑖𝜋))")]
[Arguments(@"\text{a|b}", @"\text{a|b}", @"""a|b""")]
[Arguments(@"a\vert b", @"a|b", @"𝑎\|𝑏")]
[Arguments(@"\vert x\vert", @"|x|", @"|𝑥|")]
Expand Down
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