lojix/logic/src/main/com/thesett/aima/logic/fol/OpSymbol.java
public int compareTo(Object o)
    {
        OpSymbol opSymbol = (OpSymbol) o;

        return (priority < opSymbol.priority) ? -1 : ((priority > opSymbol.priority) ? 1 : 0);
    }
public int compareTo(Object o)
    {
        OpSymbol opSymbol = (OpSymbol) o;

        return (priority < opSymbol.priority) ? -1 : ((priority > opSymbol.priority) ? 1 : 0);
    }
Compares this object with the specified object for order, providing a negative integer, zero, or a positive
integer as this symbols priority is less than, equal to, or greater than the comparator. If this symbol is 'less'
than another that means that it has a lower priority value, which means that it binds more tightly.

@param  o The object to be compared with.

@return A negative integer, zero, or a positive integer as this symbols priority is less than, equal to, or
greater than the comparator.