title: Reduce, fold or scan (Left/Right)?
body: <p>When should I use <code>reduceLeft</code>, <code>reduceRight</code>, <code>foldLeft</code>, <code>foldRight</code>, <code>scanLeft</code> or <code>scanRight</code>?</p>
  
  <p>I want an intuition/overview of their differences - possibly with some simple examples.</p>