xiiregexbuilder

commit b37fdb4f722532ac3630160ba9fc41fdea36e368
parent 491dc5bb2a0e3001b1a2f55203861697610ce06e
Author: Pranav Prabhu Kumble <kumblepranavprabhu@gmail.com>
Date:   Tue, 31 Mar 2026 00:46:09 +0530

Week 2: Implement AST Parser (Part 3: Finalizing)

Diffstat:
M
src/parser.cpp
 | 
30
++++++++++++++++++++++++++++++
M
src/parser.h
 | 
25
+++++++++++++++++++++++++

2 files changed, 55 insertions(+), 0 deletions(-)
diff --git a/src/parser.cpp b/src/parser.cpp
@@ -98,3 +98,33 @@ std::unique_ptr<ASTNode> Parser::parseAtom() {
     return nullptr; // Should not reach here
 }
 
+const Token& Parser::peek() const {
+    return tokens[pos];
+}
+
+const Token& Parser::advance() {
+    if (!isAtEnd()) pos++;
+    return tokens[pos - 1];
+}
+
+bool Parser::match(TokenType type) {
+    if (check(type)) {
+        advance();
+        return true;
+    }
+    return false;
+}
+
+bool Parser::check(TokenType type) const {
+    if (isAtEnd()) return false;
+    return peek().type == type;
+}
+
+bool Parser::isAtEnd() const {
+    return pos >= tokens.size() || tokens[pos].type == TokenType::END_OF_INPUT;
+}
+
+void Parser::error(const std::string& message) const {
+    const Token& t = peek();
+    throw std::runtime_error(message + " at line " + std::to_string(t.line) + ", column " + std::to_string(t.column));
+}
diff --git a/src/parser.h b/src/parser.h
@@ -80,3 +80,28 @@ public:
     explicit OptionalNode(std::unique_ptr<ASTNode> i)
         : ASTNode(ASTNodeType::OPTIONAL), inner(std::move(i)) {}
 };
+
+class Parser {
+public:
+    explicit Parser(const std::vector<Token>& tokens);
+    std::unique_ptr<ASTNode> parse();
+
+private:
+    const std::vector<Token>& tokens;
+    size_t pos;
+
+    std::unique_ptr<ASTNode> parseExpression();   // Union
+    std::unique_ptr<ASTNode> parseTerm();         // Concatenation
+    std::unique_ptr<ASTNode> parseFactor();       // Quantifiers
+    std::unique_ptr<ASTNode> parseAtom();         // Literals, Dot, Parens
+
+    const Token& peek() const;
+    const Token& advance();
+    bool match(TokenType type);
+    bool check(TokenType type) const;
+    bool isAtEnd() const;
+
+    void error(const std::string& message) const;
+};
+
+#endif // PARSER_H