title: What are one-to-one onto functions?
body: <p>We have been told about this function: a combination of a one-to-one and onto, our teacher called it ("one-to-one onto function"). But I am skeptical about it, because I can't find such word or its definition on the web. </p>
  
  <p>Maybe our teacher is mistaken about this topic; maybe it doesn't really exist.</p>
  
  <p>What do you think? </p>