xiiregexbuilder

commit 71535acc3c401f82ef63d68900a5930a2d7df7ea
parent 536594803c76145b84c19d51bc4362546e9a7bba
Author: Pranav Prabhu Kumble <kumblepranavprabhu@gmail.com>
Date:   Sat, 28 Mar 2026 17:23:04 +0530

Week 2: Implement Lexer (Part 2: Core logic)

Diffstat:
M
src/lexer.cpp
 | 
34
++++++++++++++++++++++++++++++++++
M
src/lexer.h
 | 
21
+++++++++++++++++++++

2 files changed, 55 insertions(+), 0 deletions(-)
diff --git a/src/lexer.cpp b/src/lexer.cpp
@@ -24,3 +24,37 @@ char Lexer::peek() const {
     return input[pos];
 }
 
+char Lexer::advance() {
+    char current = input[pos++];
+    col++;
+    return current;
+}
+
+bool Lexer::isAtEnd() const {
+    return pos >= input.length();
+}
+
+std::vector<Token> Lexer::tokenize() {
+    std::vector<Token> tokens;
+
+    while (!isAtEnd()) {
+        char c = peek();
+        int currentCharCol = col;
+
+        switch (c) {
+            case '.':
+                tokens.emplace_back(TokenType::DOT, advance(), line, currentCharCol);
+                break;
+            case '*':
+                tokens.emplace_back(TokenType::STAR, advance(), line, currentCharCol);
+                break;
+            case '+':
+                tokens.emplace_back(TokenType::PLUS, advance(), line, currentCharCol);
+                break;
+            case '?':
+                tokens.emplace_back(TokenType::QUESTION, advance(), line, currentCharCol);
+                break;
+            case '|':
+                tokens.emplace_back(TokenType::PIPE, advance(), line, currentCharCol);
+                break;
+            case '(':
diff --git a/src/lexer.h b/src/lexer.h
@@ -13,3 +13,24 @@ enum class TokenType {
     QUESTION,
     PIPE,
     LPAREN,
+    RPAREN,
+    END_OF_INPUT
+};
+
+struct Token {
+    TokenType type;
+    char value; // Meaningful for LITERAL, otherwise ignored or holds the char representation
+    int line;   // Useful for error reporting
+    int column; // Useful for error reporting
+
+    Token(TokenType t, char v = 0, int l = 0, int c = 0)
+        : type(t), value(v), line(l), column(c) {}
+};
+
+std::string tokenTypeToString(TokenType type);
+
+class Lexer {
+public:
+    explicit Lexer(const std::string& input, int lineNum = 0);
+    std::vector<Token> tokenize();
+