Are the bit patterns of NaNs really hardware-dependent?

Question

I was reading about floating-point NaN values in the Java Language Specification (I\'m boring). A 32-bit float has this bit format:

seee eeee em         


        

Answer 1

The only other NaN value that I could generate with normal arithmetic operations so far is the same but with the sign changed:

public static void main(String []args) {
    Double tentative1 = 0d/0d;
    Double tentative2 = Math.sqrt(-1d);
    
    System.out.println(tentative1);
    System.out.println(tentative2);
    
    System.out.println(Long.toHexString(Double.doubleToRawLongBits(tentative1)));
    System.out.println(Long.toHexString(Double.doubleToRawLongBits(tentative2)));
    
    System.out.println(tentative1 == tentative2);
    System.out.println(tentative1.equals(tentative2));
}

Output:

NaN

NaN

7ff8000000000000

fff8000000000000

false

true