title: Are Monad instances uniquely determined by their Applicative instances?
body: <p>In <a href="https://stackoverflow.com/q/32931549/1333025">To what extent are Applicative/Monad instances uniquely determined?</a> I asked if the for a given data type the instances are uniquely determined (which is not the case). However, a related but different question is:</p>
  
  <p><strong>If we have a data type with an <code>Applicative</code> instance, can it have more than one valid <code>Monad</code> instance?</strong> Or in other words, is the corresponding monad uniquely determined, if it exists?</p>