Implicit times between parentheses (#28)

* add times between closing and opening parenthesis

* bump version

* insert times

* changelog

Author: edhom

math_keyboard/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.1.4
+
+* Fixed missing implicit times operator between a closing and an opening parenthesis. 
+
 ## 0.1.3
 
 * Added new symbols icon for functions button.

math_keyboard/lib/src/foundation/tex2math.dart

@@ -129,7 +129,7 @@ class TeXParser {
 
     for (var i = 0; i < _stream.length; i++) {
       /// wrong syntax: fr fo lr lo oo (b/r postfix or wrong)
-      /// need times: bb bf bl rb rf !f !l
+      /// need times: bb bf bl rb rf rl !f !l
       /// negative number: -(bfl) / l-(bfl)
 
       // negative number
@@ -161,18 +161,49 @@ class TeXParser {
         continue;
       }
       if (i < _stream.length - 1 && _stream[i][1] == 'r') {
+        var insertTimes = false;
         switch (_stream[i + 1][1]) {
           case 'b':
           case 'f':
-            _stream.insert(i + 1, [
-              r'\times',
-              ['o', 3, 'l'],
-            ]);
-            i++;
+            insertTimes = true;
+            break;
+          case 'l':
+            // In case there is a closing parenthesis directly followed by an
+            // opening one, some further checks are necessary.
+            if (_stream[i][0] == ')' && _stream[i + 1][0] == '(') {
+              insertTimes = true;
+            } else if (_stream[i][0] == '}' && _stream[i + 1][0] == '(') {
+              // This case is unfavorable. If the '}' closes the second argument
+              // of a fraction or marks the end of an exponent, we want to
+              // insert 'times'. However, if '}' closes the base argument of a
+              // logarithm function, we don't want to insert a times symbol.
+              // That's why we have to check what's in front of the matching
+              // opening '{'.
+              final stack = ['}'];
+              var j = i - 1;
+              while (j > 0 && stack.isNotEmpty) {
+                if (_stream[j][0] == '{') {
+                  stack.removeLast();
+                } else if (_stream[j][0] == '}') {
+                  stack.add('}');
+                }
+                j--;
+              }
+              if (j >= 0 && _stream[j][0] != '_') {
+                insertTimes = true;
+              }
+            }
             break;
           default:
             break;
         }
+        if (insertTimes) {
+          _stream.insert(i + 1, [
+            r'\times',
+            ['o', 3, 'l'],
+          ]);
+          i++;
+        }
         continue;
       }
       if (i < _stream.length - 1 && _stream[i][0] == '!') {

math_keyboard/pubspec.yaml

@@ -2,7 +2,7 @@ name: math_keyboard
 description: >-2
   Math expression editing using an on-screen software keyboard or physical keyboard input in a
   typeset input field in Flutter.
-version: 0.1.3
+version: 0.1.4
 homepage: https://github.com/simpleclub/math_keyboard/tree/main/math_keyboard
 
 environment:

math_keyboard/test/foundation/tex2math_test.dart

@@ -56,6 +56,24 @@ void main() {
         Parser().parse(exp).toString(),
       );
     });
+
+    test('implicit2', () {
+      const tex = '(23)({c})';
+      const exp = '23*c';
+      expect(
+        TeXParser(tex).parse().toString(),
+        Parser().parse(exp).toString(),
+      );
+    });
+
+    test('implicit3', () {
+      const tex = '23^{2}({c})';
+      const exp = '23^2*c';
+      expect(
+        TeXParser(tex).parse().toString(),
+        Parser().parse(exp).toString(),
+      );
+    });
   });
 
   group('frac', () {
@@ -154,6 +172,15 @@ void main() {
         Parser().parse(exp).toString(),
       );
     });
+
+    test('nRoot', () {
+      const tex = r'2 \times  \sqrt[3]{{x}}';
+      const exp = '(2.0 * (x^(1.0 / 3.0)))';
+      expect(
+        TeXParser(tex).parse().toString(),
+        Parser().parse(exp).toString(),
+      );
+    });
   });
 
   group('logarithm', () {