how to debug the Expected ), Expected { and Expected statement(do, let, while, return or if) errors in jack Programming Language

Question

I am working on Jack's programming language and trying to make a hangman game code I have written the code for the game without graphical representation. but I can't find any help for debugging my code so far is

class HangmanGame {
  field String secretWord;
  field String guessedLetters;
  field int maxAttempts;
  field int attempts;

  constructor HangmanGame new(String word) {
    let secretWord = word;
    let guessedLetters = "";
    let maxAttempts = 6;
    let attempts = 0;
    return this;
  }

  method void play() {
    var String displayWord;
    var char letter;
    var int i;
    let displayWord = "";
    while (i < secretWord.length()) 
    {
      let letter = secretWord.charAt(i);
      if (guessedLetters.contains(String.valueOf(letter))) 
      {
        let displayWord = displayWord + String.valueOf(letter);
      } 
      else 
      {
        let displayWord = displayWord + "_";
      }
    let i = i + 1;
    }
    do Output.printString(displayWord);
    while (displayWord != secretWord && attempts < maxAttempts) {
      do Output.printString("\nEnter a letter: ");
      let char guess = Keyboard.readChar();
      let guessedLetters = guessedLetters + String.valueOf(guess);
      let boolean found = false;
      let int j = 0;
      while (j < secretWord.length()) {
        if (secretWord.charAt(j) == guess) {
          let found = true;
          let displayWord = displayWord.substring(0, j) + String.valueOf(guess) + displayWord.substring(j + 1);
        }
        let j = j + 1;
      }

      if (!found) {
        let attempts = attempts + 1;
        do Output.printString("Incorrect guess. Attempts remaining: " + (maxAttempts - attempts));
      }

      do Output.printString(displayWord);
    }

    do Output.printString("\nCongratulations! You guessed the word.");
  }
}

now while compiling. i have the error In HangmanGame.jack (line 34): In subroutine play: Expected ) In HangmanGame.jack (line 34): In subroutine play: Expected { In HangmanGame.jack (line 34): In subroutine play: Expected statement(do, let, while, return or if)

line 34 is while (displayWord != secretWord && attempts < maxAttempts) {

what am I doing wrong

i have tried puting brackets it removes the ) and { error but the Expected statement(do, let, while, return or if) stays tehre which make no Sense at all to me

Answer 1

Sometimes errors come up from unexpected places, and sometimes compilers get mixed up about where the error occurs. My guess is the error in this case has nothing to do with brackets, rather the statements that come after it:

let char guess = Keyboard.readChar();
let guessedLetters = guessedLetters + String.valueOf(guess);
let boolean found = false;
let int j = 0;

the let keyword is for assigning a new value to the variable, while the var keyword is used to declare variables. Unlike in java, and many other languages where you can do both at the same time, that is not true for jack. In jack you must declare all variables at the beginning of a function, and then later you can assign values (including initializing the variables) to them:

Solution

 method void play() {
    var String displayWord;
    var char letter;
    var int i;
    
    // DECLARE variables here, just like you did the ones above, including the type
    var char guess;
    var String guessedLetters;
    var boolean found;
    var int j;

    let displayWord = "";
    while (i < secretWord.length()) 
    {
      let letter = secretWord.charAt(i);
      if (guessedLetters.contains(String.valueOf(letter))) 
      {
        let displayWord = displayWord + String.valueOf(letter);
      } 
      else 
      {
        let displayWord = displayWord + "_";
      }
    let i = i + 1;
    }
    do Output.printString(displayWord);
    while (displayWord != secretWord && attempts < maxAttempts) {
      do Output.printString("\nEnter a letter: ");
      
      // NOTE: notice that here I removed the type, since that goes with the 
      // declaration of the variables
      let guess = Keyboard.readChar();
      let guessedLetters = guessedLetters + String.valueOf(guess);
      let found = false;
      let j = 0;

      while (j < secretWord.length()) {
        if (secretWord.charAt(j) == guess) {
          let found = true;
          let displayWord = displayWord.substring(0, j) + String.valueOf(guess) + displayWord.substring(j + 1);
        }
        let j = j + 1;
      }

      if (!found) {
        let attempts = attempts + 1;
        do Output.printString("Incorrect guess. Attempts remaining: " + (maxAttempts - attempts));
      }

      do Output.printString(displayWord);
    }

    do Output.printString("\nCongratulations! You guessed the word.");
  }

So why does jack not allow you to do something seemingly simple like declare and initialize a variable in one line. Simple. It makes writing the compiler a lot harder!