Syntax:

conctructors:
this (...) - another deffault ...

infix operator
any method with a parameter can be used like an infix operator
  r add s
  r less s
  r max s

like in Haskell, method can be formed of spec-chars
Note: an id can start from alphanums, end with an underscore (_), followed by spec-chars.
Note: the precedence of an operator is determined by its first character

override-specifier exists in Scala

operators:
- all operators ending with a colon (:) are associative to the right
  they are seen as method calls on right-hand operand

http://www.slideshare.net/joeygibson/operator-overloading-in-scala-2923973