64 lines
1.5 KiB
Java
64 lines
1.5 KiB
Java
package com.webcodepro.applecommander.util.applesoft;
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import java.util.Objects;
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import java.util.Queue;
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import com.webcodepro.applecommander.util.applesoft.Token.Type;
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/**
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* The Parser will read a series of Tokens and build a Program.
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* Note that this is not a compiler and does not "understand" the program.
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*/
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public class Parser {
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private final Queue<Token> tokens;
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public Parser(Queue<Token> tokens) {
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Objects.requireNonNull(tokens);
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this.tokens = tokens;
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}
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public Program parse() {
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Program program = new Program();
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while (!tokens.isEmpty()) {
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Line line = readLine();
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program.lines.add(line);
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}
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return program;
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}
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public Line readLine() {
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Line line = new Line(expectNumber());
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while (!tokens.isEmpty() && tokens.peek().type != Type.EOL) {
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Statement statement = readStatement();
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if (statement != null) {
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line.statements.add(statement);
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} else {
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break;
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}
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}
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if (!tokens.isEmpty() && tokens.peek().type == Type.EOL) {
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tokens.remove(); // Skip that EOL
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}
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return line;
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}
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public Statement readStatement() {
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Statement statement = new Statement();
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while (!tokens.isEmpty()) {
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if (tokens.peek().type == Type.EOL) break;
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Token t = tokens.remove();
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if (":".equals(t.text)) break;
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statement.tokens.add(t);
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}
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return statement;
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}
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public int expectNumber() {
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Token c = tokens.remove();
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if (c.type != Type.NUMBER) {
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throw new RuntimeException("Expected a number in line #" + c.line);
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}
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return c.number.intValue();
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}
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}
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