title: GroupBy using list of records in Elm
body: <p>What would an Elm function definition look like which takes a list of records, and perform a groupby operation (see example below)? Using a SQL analogy, I'm basically trying to achieve <code>select last, sum(age) from table group by last</code>in Elm.</p>
  
  <pre><code>[{name= "John", last= "Smith", age= 10}
        ,{name="Jason", last= "Smith", age= 9}
        , {name="Jane", last ="White", age =5}]
  
   return [{last="Smith", age =19},
           {last ="White", age =5}]
  </code></pre>