scala2-3-MonoidTypeClassNumeric3.scala

// Compare to scala2-3-MonoidTypeClassNumeric2.scala
// Anonymous givens; just remove the name!
given [T](using num: Numeric[T]): Monoid[T] with
  def unit: T = num.zero
  extension (t: T) def combine(other: T): T = num.plus(t, other)

// or use the _context bound_ syntax:
// given [T: Numeric]: Monoid[T] with
//   def unit: T = summon[Numeric[T]].zero   // Use summon to retrieve the Numeric
//   extension (t: T) def combine(other: T): T = summon[Numeric[T]].plus(t, other)

2.2 <+> (3.3 <+> 4.4)             // 9.9
(2.2 <+> 3.3) <+> 4.4             // 9.9

BigDecimal(3.14) <+> summon[Monoid[BigDecimal]].unit
summon[Monoid[BigDecimal]].unit  <+> BigDecimal(3.14)