Supplied compiler doesn't agree what is true between if statement and while statement

[bupjae]

Jack source code:

class Main {
    function void main() {
        if (1) {
            do Output.printString("If statement: 1 is true.");
        } else {
            do Output.printString("If statement: 1 is false.");
        }
        do Output.println();
        while (1) {
            do Output.printString("While statement: 1 is true.");
            return;
        }
        do Output.printString("While statement: 1 is false.");
        return;
    }
}

Expected output:

If statement: 1 is true.
While statement: 1 is true.

Actual output:

If statement: 1 is true.
While statement: 1 is false.

As I don't have *complete* Jack language specification (something like https://docs.oracle.com/javase/specs/jls/se11/html/index.html ), I'm not sure whether it should be compiler bug or not.
I have to debug ~1hr why my Math.jack is not working during Project 12 because of this :(

[cadet1620]

This is a known JackCompiler issue.

while (expression) statements must use the result of a comparison because they implement while (expression==true) where true in the Jack language is defined to be -1.

[ivant]

The problem is that for the while, the Jack compiler generates the following code:

label WHILE_EXP0
push constant 1
not
if-goto WHILE_END0
// code for the body
goto WHILE_EXP0
label WHILE_END0

The problem is, that not is a bitwise negation, not logical one. So, it will replace the 1 at the top of the stack with 1111111111111110, which is different than 0 so the if-goto will not jump. The code generated for if doesn't use the negation, even though the book suggests it's the way to compile it, hence the difference.

bupjae wrote

I have to debug ~1hr why my Math.jack is not working during Project 12 because of this :(

This is not a waste of time! You learned a lot in that 1 hour.