title: Map, Filter, Foldr in DrRacket/Scheme
body: <p>Programming language: Scheme/DrRacket</p>
  
  <p>We're currently going over <code>map</code>, <code>filter</code>, and <code>foldr</code> in my comp sci class. I understand that all three can be used to create abstract functions, but I am honestly a little confused about the difference between the three and when I'd use each one. </p>
  
  <p>Anyone care to explain what each is used for and how they are different? Unfortunately my book is not very clear.</p>