The official Jack compiler didn't automatically convert int to char ?

[social_loser]

I'm trying to write the String class. In chapter 9, section 9.2.3, the book said assign a int to a char is allowed. So I use it  to write the String Class in project 12.
Following is my String.setInt() method.
    method void setInt(int number) {
        var int i;
        var int neg;
        var char c ;
        var int remain;
        var int pass;
        let pass = number;    // save the original number for pass to the next call.
        let neg=0;
        if (number < 0){
            let neg=1;
            let number = Math.abs(number);
        }
        let remain= number - (number / 10 * 10 ) ;
        let c= remain + 48;
        if (number < 10 ){
            do setCharAt(0,0);
            if (neg=1) {
                do appendChar("-");
            }
            do appendChar(c);
            return ;
        }
        do setInt( pass / 10 );
        do appendChar(c);
        return ;
    }

but when I 'm trying to use the official compiler to compile it , there comes an error message :

In String.jack (line 89): In subroutine setInt: a char value is expected

so did I misunderstand it ?  is auto-convert only allowed when the right side is constant ?

[cadet1620]

    var char c ;
    var int remain;
    ...
    let remain= number - (number / 10 * 10 ) ;

    let c= remain + 48;    // "In subroutine setInt: a char value is expected"

This is a compiler bug. Jack is supposed to be an untyped language so this construct should be legal.

You can change c to an "int".


Also note that "-" creates a String object not a char constant. You need to use the numeric value of the '-' character:

    do appendChar(45);

--Mark

[social_loser]

thank you for your reply. I changed type of c to be 'int' and have passed it now. however , code :

        var char c ;
        var int remain;
        let remain=remain+48;
        let c= remain;

still not being allowed. I write a test class :

class Test {
        function void test(){
                var char c ;
                var int remain;
                let remain= 20;
                let c= remain;
                return ;
        }
}

won't compile too. so the official compiler do some check the variable type. only assigning a integerConstant to a char is allowed.

[cadet1620]

Thanks, I updated my post.

--Mark

[Ichiro]

Hi,

I tried to output a letter on the screen by using the printChar function, but it seems I cannot substitute a letter for a variable. Following is my main function code and when I compiled it, it returned the error message on the line of "let ~" as shown below.

class Main {
   function void main() {  
      var char a;  
      let a='r';                             #In subroutine main: Expected - or ~ or ( in term
      do Output.printChar(a);
    return;
   }
}


Another thing that puzzled me was when I substituted an int constant for a char variable, the function printChar did not work while the function printInt succeded as shown below.

class Main {
   function void main() {  
      var char a;  
      let a=3;
      do Output.printInt(a);
    return;
   }
}


As I am just writing some programs to get used to the Jack language, I can forget about them and work on other kinds of programs without using them. I just wanted to confirm that these were because of the compiler bugs.

Thanks,
Ichiro

[WBahn]

The Jack language specification has no support for character literals. This would not be terribly difficult to implement, but would greatly increase the level of difficultly for many students.