package recur;

public class ParserG {
    Letter input;
    char next;
    public ParserG() { }

    public boolean analys(String word) {
        input = new Letter(word);
        try {
            next = input.nextChar();
            S();
            match('$');
        } catch (SyntaxError ex) {
            System.out.println(ex.getMessage());
            return false;
        }
        return true;
    }
    private void S() throws SyntaxError {
        match('a');
        match('b');
        if (next == 'b') {
            match('b');
        } else {
            A();
            B();
            match('d');
        }

    }

    private void A() throws SyntaxError {
        if (next == 'a') {
            next = input.nextChar();
            A();
            match('b');
        } else {
            match('d');
        }
    }

    private void B() throws SyntaxError {
        if (next == 'b') {
            match('b');
        } else {
            next = input.nextChar();
            B();
            match('c');
            A();
        }
    }
    private void match(char c) throws SyntaxError {
        if (next == c) {
            next = input.nextChar();
        }
        else throw new SyntaxError("Expecting " + c + ", found " + next);
    }
}