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‎README.md

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# Crafting Interpreter

‎lox/.idea/.gitignore

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‎lox/.idea/misc.xml

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‎lox/.idea/modules.xml

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‎lox/example/basic.lox

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print "Hello, world!";
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true;
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false;
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1234;
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12.34;
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"I am a string";
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"";
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"123";
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nil;
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add + me;
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subtract - me;
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multiply * me;
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divide / me;
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-negateMe;
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less < than;
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lessThan <= orEqual;
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greater > than;
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greaterThan >= orEqual;
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1 == 2;
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"cat" != "dog";
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314 == "pi";
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123 == "123";
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!true;
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!false;
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true and false;
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true and true;
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false or false;
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true or false;
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var average = (min + max) / 2;
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{
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print "one statement.";
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print "two statements.";
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}
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var a = "hello";
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var b;
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print a;
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if (condition) {
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print "yes";
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} else {
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print "no";
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}
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var a = 1;
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while (a < 10) {
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print a;
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a = a + 1;
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}
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for (var a = 1; a < 10; a = a + 1) {
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print a;
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}
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makeBreakfast(bacon, egg, toast);
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makeBreakfast();
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fun printSum(a, b) {
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print a + b;
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}
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fun returnSum(a, b) {
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return a + b;
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}
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class Breakfast {
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cook() { print "Eggs a-fryin'!"; }
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serve(who) { print "Enjoy your breakfast, " + who + "."; }
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}

‎lox/lox.iml

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<?xml version="1.0" encoding="UTF-8"?>
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<module type="JAVA_MODULE" version="4">
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<component name="NewModuleRootManager" inherit-compiler-output="true">
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<exclude-output />
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<content url="file://$MODULE_DIR$">
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<sourceFolder url="file://$MODULE_DIR$/src" isTestSource="false" />
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</content>
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<orderEntry type="inheritedJdk" />
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<orderEntry type="sourceFolder" forTests="false" />
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</component>
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</module>

‎lox/out/production/lox/com/craftinginterpreters/lox/Lox.class

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‎lox/out/production/lox/com/craftinginterpreters/lox/Scanner.class

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‎lox/out/production/lox/com/craftinginterpreters/lox/Token.class

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‎lox/out/production/lox/com/craftinginterpreters/lox/TokenType.class

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‎lox/src/com/craftinginterpreters/lox/Lox.java

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package com.craftinginterpreters.lox;
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import java.io.BufferedReader;
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import java.io.IOException;
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import java.io.InputStreamReader;
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import java.nio.charset.Charset;
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import java.nio.file.Files;
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import java.nio.file.Paths;
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import java.util.List;
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public class Lox {
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static boolean hadError = false;
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public static void main(String[] args) throws IOException {
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if (args.length > 1) {
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System.out.println("Usage: jlox [script]");
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} else if (args.length == 1) {
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runFile(args[0]);
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} else {
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runPrompt();
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}
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}
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private static void runFile(String path) throws IOException {
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byte[] bytes = Files.readAllBytes(Paths.get(path));
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run(new String(bytes, Charset.defaultCharset()));
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if (hadError) System.exit(65);
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}
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private static void runPrompt() throws IOException {
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InputStreamReader input = new InputStreamReader(System.in);
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BufferedReader reader = new BufferedReader(input);
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for (;;) {
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System.out.print("> ");
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String line = reader.readLine();
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if (line == null) break;
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run(line);
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hadError = false;
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}
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}
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private static void run(String source) {
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Scanner scanner = new Scanner(source);
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List<Token> tokens = scanner.scanTokens();
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for (Token token: tokens) {
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System.out.println(token);
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}
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}
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static void error(int line, String message) {
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report(line, "", message);
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}
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private static void report(int line, String where, String message) {
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System.err.println("[line " + line + "] Error" + where + ": " + message);
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hadError = true;
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}
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}

‎lox/src/com/craftinginterpreters/lox/Scanner.java

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package com.craftinginterpreters.lox;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import static com.craftinginterpreters.lox.TokenType.*;
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public class Scanner {
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private final String source;
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private int start = 0;
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private int current = 0;
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private int line = 1;
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private final List<Token> tokens = new ArrayList<>();
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private static final Map<String, TokenType> keywords;
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static {
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keywords = new HashMap<>();
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keywords.put("and", AND);
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keywords.put("class", CLASS);
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keywords.put("else", ELSE);
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keywords.put("false", FALSE);
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keywords.put("for", FOR);
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keywords.put("fun", FUN);
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keywords.put("if", IF);
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keywords.put("nil", NIL);
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keywords.put("or", OR);
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keywords.put("print", PRINT);
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keywords.put("return", RETURN);
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keywords.put("super", SUPER);
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keywords.put("this", THIS);
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keywords.put("true", TRUE);
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keywords.put("var", VAR);
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keywords.put("while", WHILE);
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}
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Scanner(String source) {
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this.source = source;
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}
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List<Token> scanTokens() {
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while (!isAtEnd()) {
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start = current;
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// [start, current)
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scanToken();
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}
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tokens.add(new Token(EOF, "", null, line));
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return tokens;
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}
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private void scanToken() {
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char c = advance();
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switch (c) {
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case '(': addToken(LEFT_PAREN); break;
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case ')': addToken(RIGHT_PAREN); break;
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case '{': addToken(LEFT_BRACE); break;
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case '}': addToken(RIGHT_BRACE); break;
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case ',': addToken(COMMA); break;
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case '.': addToken(DOT); break;
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case '-': addToken(MINUS); break;
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case '+': addToken(PLUS); break;
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case ';': addToken(SEMICOLON); break;
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case '*': addToken(STAR); break;
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case '!':
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addToken(match('=') ? BANG_EQUAL : BANG);
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break;
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case '=':
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addToken(match('=') ? EQUAL_EQUAL : EQUAL);
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break;
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case '<':
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addToken(match('=') ? LESS_EQUAL : LESS);
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break;
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case '>':
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addToken(match('=') ? GREATER_EQUAL : GREATER);
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break;
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case '/':
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if (match('/')) {
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// this is comment! until the end of this line
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while (peek() != '\n' && !isAtEnd()) advance();
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} else {
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addToken(SLASH);
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}
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break;
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case '\n':
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line++;
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case ' ':
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case '\r':
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case '\t':
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break;
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case '"': string(); break;
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default:
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if (isDigit(c)) {
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number();
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} else if (isAlpha(c)) {
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identifier();
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} else {
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Lox.error(line, "Unexpected character.");
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}
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break;
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}
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}
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private void identifier() {
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while (isAlphaNumeric(peek())) advance();
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String text = source.substring(start, current);
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TokenType type = keywords.get(text);
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if (type == null) {
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addToken(IDENTIFIER);
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} else {
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addToken(type);
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}
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}
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private static boolean isDigit(char c) {
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return c >= '0' && c <= '9';
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}
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private static boolean isAlpha(char c) {
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return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') || (c == '_');
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}
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private static boolean isAlphaNumeric(char c) {
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return isAlpha(c) || isDigit(c);
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}
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private void number() {
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while (isDigit(peek())) {
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advance();
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}
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if (peek() == '.' && isDigit(peekNext())) {
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advance();
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while (isDigit(peek())) advance();
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}
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addToken(NUMBER, Double.parseDouble(source.substring(start, current)));
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}
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private void string() {
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// continue until we find the closing "
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while (peek() != '"' && !isAtEnd()) {
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if (peek() == '\n') line++;
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advance();
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}
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if (isAtEnd()) {
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Lox.error(line, "Unterminated string.");
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return;
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}
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advance();
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String value = source.substring(start + 1, current - 1);
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addToken(STRING, value);
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}
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private char peek() {
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// lookahead
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if (isAtEnd()) return '\0';
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return source.charAt(current);
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}
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private char peekNext() {
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if (current + 1 >= source.length()) return '\0';
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return source.charAt(current + 1);
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}
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private boolean match(char expected) {
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//
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if (isAtEnd()) return false;
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if (source.charAt(current) == expected) {
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current++;
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return true;
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}
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return false;
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}
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private char advance() {
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current++;
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return source.charAt(current - 1);
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}
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private void addToken(TokenType type) {
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addToken(type, null);
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}
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private void addToken(TokenType type, Object literal) {
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String text = source.substring(start, current);
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tokens.add(new Token(type, text, literal, line));
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}
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private boolean isAtEnd() {
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return current >= source.length();
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}
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}

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