add support for multiplying parentheses (#87)

* add support for multiplying parentheses * fix code review details * clean code --------- Co-authored-by: Juan carlos Vallejo salazar <juancarlosvallejosalazar@Mac-mini-de-Juan.local>
fkleon · Jul 31, 2024 · 35992ba · 35992ba
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [2.5.1] - 2024-05-23
+
+### Added
+
+- Add support for multiplying parentheses
+
 ## [2.5.0] - 2024-04-16
 
 ### Added

diff --git a/lib/src/parser.dart b/lib/src/parser.dart
@@ -16,17 +16,21 @@ class Parser {
   Parser() : lex = Lexer();
   Map<String, dynamic> functionHandlers = <String, dynamic>{};
 
-  /// Parses the given input string into an [Expression]. Throws a
-  /// [ArgumentError] if the given [inputString] is empty. Throws a
-  /// [StateError] if the token stream is invalid. Returns a valid
-  /// [Expression].
-  Expression parse(String inputString) {
+  /// Parses the given input string into an [Expression]. If
+  /// [multiplyWithParentheses] is true you can multiply using
+  /// parentheses. Throws  [ArgumentError] if the given [inputString]
+  /// is empty. Throws a [StateError] if the token stream is
+  /// invalid. Returns a valid [Expression].
+  Expression parse(String inputString, {bool multiplyWithParentheses = false}) {
     if (inputString.trim().isEmpty) {
       throw FormatException('The given input string was empty.');
     }
 
     final List<Expression> exprStack = <Expression>[];
-    final List<Token> inputStream = lex.tokenizeToRPN(inputString);
+    final List<Token> inputStream = lex.tokenizeToRPN(
+      inputString,
+      multiplyWithParentheses: multiplyWithParentheses,
+    );
 
     for (Token currToken in inputStream) {
       Expression currExpr, left, right;
@@ -208,7 +212,8 @@ class Lexer {
 
   /// Tokenizes a given input string.
   /// Returns a list of [Token] in infix notation.
-  List<Token> tokenize(String inputString) {
+  List<Token> tokenize(String inputString,
+      {bool multiplyWithParentheses = false}) {
     final List<Token> tempTokenStream = <Token>[];
     final String clearedString = inputString.replaceAll(' ', '').trim();
     final RuneIterator iter = clearedString.runes.iterator;
@@ -299,6 +304,27 @@ class Lexer {
       // There are no more symbols in the input string but there is still a variable or keyword in the varBuffer
       _doVarBuffer(tempTokenStream);
     }
+    if (multiplyWithParentheses) {
+      for (int i = 0; i < tempTokenStream.length; i++) {
+        if (tempTokenStream[i].type == TokenType.RBRACE &&
+            i != tempTokenStream.length - 1) {
+          final nextSymbol = tempTokenStream[i + 1];
+          if ([
+            TokenType.RBRACE,
+            TokenType.DIV,
+            TokenType.TIMES,
+            TokenType.MINUS,
+            TokenType.PLUS,
+            TokenType.MOD,
+          ].every((element) => nextSymbol.type != element)) {
+            tempTokenStream.insert(
+              i + 1,
+              Token('*', TokenType.TIMES),
+            );
+          }
+        }
+      }
+    }
     return tempTokenStream;
   }
 
@@ -465,8 +491,12 @@ class Lexer {
   /// This method invokes the createTokenStream methode to create an infix token
   /// stream and then invokes the shunting yard method to transform this stream
   /// into a RPN (reverse polish notation) token stream.
-  List<Token> tokenizeToRPN(String inputString) {
-    final List<Token> infixStream = tokenize(inputString);
+  List<Token> tokenizeToRPN(String inputString,
+      {bool multiplyWithParentheses = false}) {
+    final List<Token> infixStream = tokenize(
+      inputString,
+      multiplyWithParentheses: multiplyWithParentheses,
+    );
     return shuntingYard(infixStream);
   }
 }

diff --git a/test/parser_test_set.dart b/test/parser_test_set.dart
@@ -27,6 +27,7 @@ class ParserTests extends TestSet {
         'Power': parsePower,
         'Modulo': parseModulo,
         'Multiplication': parseMultiplication,
+        'MultiplicationWithParentheses': parseMultiplicationWithParentheses,
         'Division': parseDivision,
         'Addition': parsePlus,
         'Subtraction': parseMinus,
@@ -49,10 +50,19 @@ class ParserTests extends TestSet {
 
   Parser parser = Parser();
 
-  void parameterized(Map<String, Expression> cases) {
+  void parameterized(Map<String, Expression> cases,
+      {bool multiplyWithParentheses = false}) {
     cases.forEach((key, value) {
-      test('$key -> $value',
-          () => expect(parser.parse(key).toString(), value.toString()));
+      test(
+          '$key -> $value',
+          () => expect(
+              parser
+                  .parse(
+                    key,
+                    multiplyWithParentheses: multiplyWithParentheses,
+                  )
+                  .toString(),
+              value.toString()));
     });
   }
 
@@ -127,6 +137,14 @@ class ParserTests extends TestSet {
     parameterized(cases);
   }
 
+  void parseMultiplicationWithParentheses() {
+    var cases = {
+      '(5)(5)': Number(5) * Number(5),
+      '(-2.0)5': -Number(2.0) * Number(5),
+    };
+    parameterized(cases, multiplyWithParentheses: true);
+  }
+
   void parseDivision() {
     var cases = {
       '0 / 1': Number(0) / Number(1),