Parser: Add options to configure parser behaviour

Move multiplyWithParentheses flag into options and rename to implicitMultiplication. Add lexer tests for implicit multiplication.
fkleon · Jul 31, 2024 · f196cbc · f196cbc
1 parent 35992ba
commit f196cbc
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -5,11 +5,11 @@ 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
+## [unreleased] - 2024-05-23
 
 ### Added
 
-- Add support for multiplying parentheses
+- Add parser support for implicit multiplication (thanks [juca1331](https://github.com/juca1331))
 
 ## [2.5.0] - 2024-04-16
 

diff --git a/lib/src/parser.dart b/lib/src/parser.dart
@@ -13,23 +13,23 @@ class Parser {
   final Lexer lex;
 
   /// Creates a new parser.
-  Parser() : lex = Lexer();
+  /// The given [options] can be used to configure the behaviour.
+  Parser([ParserOptions options = const ParserOptions()])
+      : lex = Lexer(options);
   Map<String, dynamic> functionHandlers = <String, dynamic>{};
 
-  /// Parses the given input string into an [Expression]. If
-  /// [multiplyWithParentheses] is true you can multiply using
-  /// parentheses. Throws  [ArgumentError] if the given [inputString]
+  /// 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, {bool multiplyWithParentheses = false}) {
+  Expression parse(String inputString) {
     if (inputString.trim().isEmpty) {
       throw FormatException('The given input string was empty.');
     }
 
     final List<Expression> exprStack = <Expression>[];
     final List<Token> inputStream = lex.tokenizeToRPN(
       inputString,
-      multiplyWithParentheses: multiplyWithParentheses,
     );
 
     for (Token currToken in inputStream) {
@@ -164,6 +164,13 @@ class Parser {
   }
 }
 
+class ParserOptions {
+  /// If [implicitMultiplication] is true the parser will allow
+  /// implicit multiplication using parentheses.
+  final bool implicitMultiplication;
+  const ParserOptions({this.implicitMultiplication = false});
+}
+
 /// The lexer creates tokens (see [TokenType] and [Token]) from an input string.
 /// The input string is expected to be in
 /// [infix notation form](https://en.wikipedia.org/wiki/Infix_notation).
@@ -173,14 +180,16 @@ class Parser {
 class Lexer {
   final Map<String, TokenType> keywords = <String, TokenType>{};
 
+  final ParserOptions options;
+
   /// Buffer for numbers
   String intBuffer = '';
 
   /// Buffer for variable and function names
   String varBuffer = '';
 
   /// Creates a new lexer.
-  Lexer() {
+  Lexer([this.options = const ParserOptions()]) {
     keywords['+'] = TokenType.PLUS;
     keywords['-'] = TokenType.MINUS;
     keywords['*'] = TokenType.TIMES;
@@ -212,8 +221,7 @@ class Lexer {
 
   /// Tokenizes a given input string.
   /// Returns a list of [Token] in infix notation.
-  List<Token> tokenize(String inputString,
-      {bool multiplyWithParentheses = false}) {
+  List<Token> tokenize(String inputString) {
     final List<Token> tempTokenStream = <Token>[];
     final String clearedString = inputString.replaceAll(' ', '').trim();
     final RuneIterator iter = clearedString.runes.iterator;
@@ -304,7 +312,7 @@ 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) {
+    if (options.implicitMultiplication) {
       for (int i = 0; i < tempTokenStream.length; i++) {
         if (tempTokenStream[i].type == TokenType.RBRACE &&
             i != tempTokenStream.length - 1) {
@@ -491,11 +499,9 @@ 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,
-      {bool multiplyWithParentheses = false}) {
+  List<Token> tokenizeToRPN(String inputString) {
     final List<Token> infixStream = tokenize(
       inputString,
-      multiplyWithParentheses: multiplyWithParentheses,
     );
     return shuntingYard(infixStream);
   }

diff --git a/test/lexer_test_set.dart b/test/lexer_test_set.dart
@@ -21,6 +21,7 @@ class LexerTests extends TestSet {
         'Power': tokenizePower,
         'Modulo': tokenizeModulo,
         'Multiplication': tokenizeMultiplication,
+        'ImplicitMultiplication': tokenizeImplicitMultiplication,
         'Division': tokenizeDivision,
         'Plus': tokenizePlus,
         'Minus': tokenizeMinus,
@@ -39,7 +40,7 @@ class LexerTests extends TestSet {
   @override
   void initTests() {}
 
-  Lexer lex = Lexer();
+  final Lexer lex = Lexer();
 
   // Test RPN
   void parameterizedRpn(Map<String, List<Token>> cases) {
@@ -50,14 +51,18 @@ class LexerTests extends TestSet {
   }
 
   /// Test infix and RPN
-  void parameterized(Map<String, (List<Token>, List<Token>)> cases) {
+  void parameterized(Map<String, (List<Token> infix, List<Token> rpn)> cases,
+      {Lexer? lexer}) {
+    lexer ??= this.lex;
     cases.forEach((expression, value) {
       var (infix, rpn) = value;
       test('$expression -> $infix -> $rpn', () {
-        var infixStream = lex.tokenize(expression);
-        expect(infixStream, orderedEquals(infix));
-        var rpnStream = lex.shuntingYard(infixStream);
-        expect(rpnStream, orderedEquals(rpn));
+        var infixStream = lexer!.tokenize(expression);
+        expect(infixStream, orderedEquals(infix),
+            reason: 'Incorrect infix notation');
+        var rpnStream = lexer.shuntingYard(infixStream);
+        expect(rpnStream, orderedEquals(rpn),
+            reason: "Incorrect reverse polish notation");
       });
     });
   }
@@ -218,6 +223,45 @@ class LexerTests extends TestSet {
     parameterized(cases);
   }
 
+  void tokenizeImplicitMultiplication() {
+    var cases = {
+      '(0)(1)': (
+        [
+          Token('(', TokenType.LBRACE),
+          Token('0', TokenType.VAL),
+          Token(')', TokenType.RBRACE),
+          Token('*', TokenType.TIMES),
+          Token('(', TokenType.LBRACE),
+          Token('1', TokenType.VAL),
+          Token(')', TokenType.RBRACE),
+        ],
+        [
+          Token('0', TokenType.VAL),
+          Token('1', TokenType.VAL),
+          Token('*', TokenType.TIMES)
+        ]
+      ),
+      '(-2.0)5': (
+        [
+          Token('(', TokenType.LBRACE),
+          Token('-', TokenType.MINUS),
+          Token('2.0', TokenType.VAL),
+          Token(')', TokenType.RBRACE),
+          Token('*', TokenType.TIMES),
+          Token('5', TokenType.VAL),
+        ],
+        [
+          Token('2.0', TokenType.VAL),
+          Token('-', TokenType.UNMINUS),
+          Token('5', TokenType.VAL),
+          Token('*', TokenType.TIMES),
+        ]
+      ),
+    };
+    var lexer = Lexer(ParserOptions(implicitMultiplication: true));
+    parameterized(cases, lexer: lexer);
+  }
+
   void tokenizeDivision() {
     var cases = {
       '0 / 1': (

diff --git a/test/parser_test_set.dart b/test/parser_test_set.dart
@@ -27,7 +27,7 @@ class ParserTests extends TestSet {
         'Power': parsePower,
         'Modulo': parseModulo,
         'Multiplication': parseMultiplication,
-        'MultiplicationWithParentheses': parseMultiplicationWithParentheses,
+        'ImplicitMultiplication': parseImplicitMultiplication,
         'Division': parseDivision,
         'Addition': parsePlus,
         'Subtraction': parseMinus,
@@ -50,16 +50,15 @@ class ParserTests extends TestSet {
 
   Parser parser = Parser();
 
-  void parameterized(Map<String, Expression> cases,
-      {bool multiplyWithParentheses = false}) {
+  void parameterized(Map<String, Expression> cases, {Parser? parser}) {
+    parser ??= this.parser;
     cases.forEach((key, value) {
       test(
           '$key -> $value',
           () => expect(
-              parser
+              parser!
                   .parse(
                     key,
-                    multiplyWithParentheses: multiplyWithParentheses,
                   )
                   .toString(),
               value.toString()));
@@ -137,12 +136,13 @@ class ParserTests extends TestSet {
     parameterized(cases);
   }
 
-  void parseMultiplicationWithParentheses() {
+  void parseImplicitMultiplication() {
     var cases = {
       '(5)(5)': Number(5) * Number(5),
       '(-2.0)5': -Number(2.0) * Number(5),
     };
-    parameterized(cases, multiplyWithParentheses: true);
+    var parser = Parser(ParserOptions(implicitMultiplication: true));
+    parameterized(cases, parser: parser);
   }
 
   void parseDivision() {