From 9e35ddee6a9251148918d176d28d7b325dd3ff79 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=BAnar=20Berg?= <runarberg@zoho.com>
Date: Wed, 24 Jun 2026 11:38:18 -0700
Subject: [PATCH] Fix scanner missing the `o.` operator

fixes #162
---
 demo/test-cases.html                          |   1 +
 src/compiler/tokenizer/scanners/alpha.js      |   4 ++--
 src/compiler/tokenizer/scanners/alpha.test.js |  18 ++++++++++++++++++
 .../tokenizer/scanners/operator.test.js       |   8 ++++++++
 test/operators.js                             |   6 ++++++
 test/snapshots/operators.js.md                |  10 ++++++++++
 test/snapshots/operators.js.snap              | Bin 1168 -> 1213 bytes
 7 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/demo/test-cases.html b/demo/test-cases.html
index 4348358..df780a0 100644
--- a/demo/test-cases.html
+++ b/demo/test-cases.html
@@ -92,6 +92,7 @@ <h2>Operators</h2>
         <test-case>ı.^\^</test-case>
         <test-case>x.^ \(n)</test-case>
         <test-case>&lt;&lt;&lt; [] &gt;&gt;&gt;</test-case>
+        <test-case>a o. b</test-case>
 
         <test-case display="block">
           \`lim sup`._(n -> oo)
diff --git a/src/compiler/tokenizer/scanners/alpha.js b/src/compiler/tokenizer/scanners/alpha.js
index 37f561e..d45a60f 100644
--- a/src/compiler/tokenizer/scanners/alpha.js
+++ b/src/compiler/tokenizer/scanners/alpha.js
@@ -30,8 +30,8 @@ export default function alphaScanner(char, input, { start, grouping }) {
     [nextChar] = input.slice(i);
   }
 
-  // alpha may contain a period, but not never end with one.
-  if (value.endsWith(".")) {
+  // alpha may contain a period, but only known ops can end with one.
+  if (value.endsWith(".") && !KNOWN_OPS.has(value)) {
     value = value.slice(0, -1);
   }
 
diff --git a/src/compiler/tokenizer/scanners/alpha.test.js b/src/compiler/tokenizer/scanners/alpha.test.js
index e92485c..1926f44 100644
--- a/src/compiler/tokenizer/scanners/alpha.test.js
+++ b/src/compiler/tokenizer/scanners/alpha.test.js
@@ -138,6 +138,24 @@ test("can’t end with a period", (t) => {
   t.is(token?.split, true);
 });
 
+test("unless it is a known operator", (t) => {
+  const token = alpha("o", "o.", { start: 0, grouping: false });
+
+  t.is(token?.type, "operator");
+  t.is(token?.value, "⊙");
+  t.is(token?.end, 2);
+  t.falsy(token?.split);
+});
+
+test("known operator ends in period cannot be followed by an alphanum", (t) => {
+  const token = alpha("o", "o.o", { start: 0, grouping: false });
+
+  t.is(token?.type, "ident");
+  t.is(token?.value, "o");
+  t.is(token?.end, 1);
+  t.is(token?.split, true);
+});
+
 test("known prefix", (t) => {
   const token = alpha("h", "hat a", { start: 0, grouping: false });
 
diff --git a/src/compiler/tokenizer/scanners/operator.test.js b/src/compiler/tokenizer/scanners/operator.test.js
index acb37cf..b67e08a 100644
--- a/src/compiler/tokenizer/scanners/operator.test.js
+++ b/src/compiler/tokenizer/scanners/operator.test.js
@@ -30,6 +30,14 @@ test("known operator", (t) => {
   t.is(token?.end, 3);
 });
 
+test("known operator that ends with a period", (t) => {
+  const token = operator("o.", " o. b", { start: 1, grouping: false });
+
+  t.is(token?.type, "operator");
+  t.is(token?.value, "⊙");
+  t.is(token?.end, 3);
+});
+
 test("emits the longest possible known operator", (t) => {
   const token = operator("^", "^^^ 1", { start: 0, grouping: false });
 
diff --git a/test/operators.js b/test/operators.js
index 39b9996..7bc7044 100644
--- a/test/operators.js
+++ b/test/operators.js
@@ -33,6 +33,12 @@ test("i hat", (t) => {
   t.snapshot(render("ı.^\\^"));
 });
 
+test("circumpunct", (t) => {
+  t.is(render("o."), "<math><mo>⊙</mo></math>");
+  t.snapshot(render("a o. b"));
+  t.snapshot(render("a o.b"));
+});
+
 test("Norm of two parallel lines", (t) => {
   t.snapshot(render("||a || b||"));
 });
diff --git a/test/snapshots/operators.js.md b/test/snapshots/operators.js.md
index 271c68e..f7440dd 100644
--- a/test/snapshots/operators.js.md
+++ b/test/snapshots/operators.js.md
@@ -36,6 +36,16 @@ Generated by [AVA](https://avajs.dev).
 
     '<math><mover><mi>ı</mi><mo>^</mo></mover></math>'
 
+## circumpunct
+
+> Snapshot 1
+
+    '<math><mi>a</mi><mo>⊙</mo><mi>b</mi></math>'
+
+> Snapshot 2
+
+    '<math><mi>a</mi><mrow><mi>o</mi><mo>.</mo><mi>b</mi></mrow></math>'
+
 ## Norm of two parallel lines
 
 > Snapshot 1
diff --git a/test/snapshots/operators.js.snap b/test/snapshots/operators.js.snap
index 63dab0ccc8ca3a5c30729b97263577bca0120a63..1858c05e94c8d7e607cf65efbc212e7a49a41883 100644
GIT binary patch
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