@Override
    default int compare(T first, T second) {
        final E a = apply(first);
        final E b = apply(second);
        if (a == null) {
            return (b == null) ? -1 : 0;
        } else {
            return a.compareTo(b);
        }
    }
Returns an alternative expression that represents the {@link Enum#name()}
of the enum that would otherwise have been returned by this expression.
<p>
If this expression would have returned {@code null}, then the new
expression will also evaluate to {@code null}.

@return  the name expression
runtime-parent/runtime-compute/src/main/java/com/speedment/runtime/compute/ToEnumNullable.java