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week5 kodutöö lahendus
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‎sols/week5/AktkHandwrittenLexer.java‎

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package week5;
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import java.io.IOException;
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import java.io.Reader;
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import java.io.UncheckedIOException;
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import java.nio.charset.StandardCharsets;
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import java.nio.file.Files;
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import java.nio.file.Path;
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import java.nio.file.Paths;
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import java.util.ArrayList;
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import java.util.List;
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import static week5.AktkToken.Type.*;
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public class AktkHandwrittenLexer {
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// Siin on meie poolt mall ette antud, millega saad kasutada praktikumist tuttavad meetodid.
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// Selle malli kasutamine ei ole kohustuslik, aga sisend antakse ette Reader liidese kaudu
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// ja viimase testi läbimiseks ei tohi sisendis liiga palju ette vaadata.
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private static final char TERMINATOR = '\0';
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private final Reader reader;
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private Character current;
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private int pos = 0;
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public AktkHandwrittenLexer(Reader input) {
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this.reader = input;
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}
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// See teeb meil testimise mugavamaks:
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public List<AktkToken> readAllTokens() {
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List<AktkToken> tokens = new ArrayList<>();
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AktkToken token;
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do {
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token = this.readNextToken();
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tokens.add(token);
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} while (token.type() != EOF);
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return tokens;
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}
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// Saame kasutada näiteks järgmiselt:
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static void main() throws IOException {
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Path path = Paths.get("inputs", "escaped.txt");
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System.out.println(Files.readString(path));
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System.out.println(new AktkHandwrittenLexer(Files.newBufferedReader(path, StandardCharsets.UTF_8)).readAllTokens());
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}
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// Siin on abimeetodid, mida soovitame kasutada.
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// Consume on sisuliselt nagu pos++ kalalekseri näites ehk läheb järgmise tähe juurde.
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private void consume() {
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if (current == TERMINATOR) {
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throw new RuntimeException("Reading passed terminator!");
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}
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read();
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pos++;
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}
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// Peek on see, mis tagastab hetkel vaadeldavat tähte.
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// (Kõige algul võib see täht olla puudu.)
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private char peek() {
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if (current == null) read();
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return current;
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}
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// See on pigem abimeetod, mis teostab tegeliku sisendist lugemist.
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// Meie enda lahenduses me seda otse ei kasuta. Kutsume ainult peek ja consume.
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private void read() {
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try {
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int i = reader.read();
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current = (i == -1) ? TERMINATOR : (char) i;
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} catch (IOException e) {
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throw new UncheckedIOException(e);
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}
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}
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/**
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* See on nüüd see oluline meetod, mida peab ise implementeerima!
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*/
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public AktkToken readNextToken() {
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while (peek() != TERMINATOR) {
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if (Character.isDigit(peek())) {
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return readInteger();
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} else if (Character.isWhitespace(peek())) {
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consume();
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} else if (peek() == '"') {
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return readString();
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} else if (Character.isLetter(peek()) || peek() == '_') {
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return readVariableOrKeyword();
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} else if (peek() == '(') {
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consume();
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return singleCharToken(LPAREN);
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} else if (peek() == ')') {
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consume();
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return singleCharToken(RPAREN);
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} else if (peek() == '+') {
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consume();
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return singleCharToken(PLUS);
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} else if (peek() == '-') {
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consume();
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return singleCharToken(MINUS);
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} else if (peek() == '*') {
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consume();
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return singleCharToken(TIMES);
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} else if (peek() == '/') {
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consume();
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if (peek() == '/') {
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consume();
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skipSingleLineComment();
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} else if (peek() == '*') {
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consume();
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skipMultiLineComment();
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} else {
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return singleCharToken(DIV);
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}
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} else {
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throw new RuntimeException("Unexpected symbol");
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}
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}
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return new AktkToken(EOF, pos, 0);
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}
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private AktkToken singleCharToken(AktkToken.Type type) {
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return new AktkToken(type, pos - 1, 1);
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}
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private void skipMultiLineComment() {
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do {
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while (peek() != '*') consume();
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consume();
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} while (peek() != '/');
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consume();
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}
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private void skipSingleLineComment() {
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while (peek() != '\n' && peek() != TERMINATOR) consume();
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}
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private AktkToken readVariableOrKeyword() {
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assert Character.isLetter(peek()) || peek() == '_';
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int initPos = this.pos;
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StringBuilder sb = new StringBuilder();
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sb.append(peek());
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consume();
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while ((Character.isLetter(peek())
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|| Character.isDigit(peek())
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|| peek() == '_')) {
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sb.append(peek());
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consume();
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}
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String content = sb.toString();
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return switch (content) {
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case "if" -> new AktkToken(IF, initPos, content.length());
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case "while" -> new AktkToken(WHILE, initPos, content.length());
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case "var" -> new AktkToken(VAR, initPos, content.length());
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default -> new AktkToken(VARIABLE, content, initPos, content.length());
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};
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}
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private AktkToken readString() {
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assert peek() == '"';
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int initPos = this.pos;
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StringBuilder sb = new StringBuilder();
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consume();
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while (peek() != '"') {
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if (peek() == '\\') {
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consume();
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switch (peek()) {
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case 'n' -> sb.append('\n');
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case 't' -> sb.append('\t');
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case '"' -> sb.append('\"');
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default -> throw new RuntimeException("Unknown character escape");
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}
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} else {
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sb.append(peek());
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}
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consume();
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}
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consume();
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return new AktkToken(STRING, sb.toString(), initPos, this.pos - initPos);
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}
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private AktkToken readInteger() {
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assert Character.isDigit(peek());
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int initPos = this.pos;
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int result = 0;
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while (Character.isDigit(peek())) {
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result = 10 * result + Character.getNumericValue(peek());
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consume();
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}
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return new AktkToken(INTEGER, result, initPos, pos - initPos);
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}
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}

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