If the operator returns in JML

Question

I need to set up a postcondition that guarantees null return if size_ is 0. Based on

 if(size_ == 0)
  return null;

how can i do this in jml? any ideas? The following does not work:

//@ ensures size_ == null ==> \return true;

early

Answer 1

Try

//@ ensures size_ == null ==> \result == true;

Example:

//@ ensures size_ == null ==> \result == true;
public boolean sizeUndefined() {
    if (size_ == null)
        return true;

    return size_.length() > 0;
}

You can also simply write it like this:

//@ ensures size_ == null ==> \result;

Here is the documentation for\result :

3.2.14 \result
\result , . , . \result , , , , .

Answer 2

: size_, Object primitive(int)?

-, ? Object primitive(boolean)?

null null, . , size_ int, return boolean, -

//@ ensures size_ == 0 ==> \result;