title: Why (copy) appending to Seq in Scala is defined as :+ and not just + as in Set and Map?
body: <p>Scala's Map and Set define a <code>+</code> operator that returns a copy of the data structure with a single element appended to it. The equivalent operator for <code>Seq</code> is denoted <code>:+</code>.</p>
  
  <p>Is there any reason for this inconsistency?</p>