SortedMapSemigroup

Given a sequence of as, combine them and return the total.

If the sequence is empty, returns None. Otherwise, returns Some(total).

Example:

scala> import cats.kernel.instances.string._

scala> Semigroup[String].combineAllOption(List("One ", "Two ", "Three"))
res0: Option[String] = Some(One Two Three)

scala> Semigroup[String].combineAllOption(List.empty)
res1: Option[String] = None

Return a combined with itself n times.

Example:

scala> import cats.kernel.instances.int._
scala> import cats.kernel.instances.string._

scala> Semigroup[Int].combineN(1, 10)
res0: Int = 10

scala> Semigroup[String].combineN("ha", 3)
res1: String = hahaha

Between each pair of elements insert middle This name matches the term used in Foldable and Reducible and a similar Haskell function.

return a semigroup that reverses the order so combine(a, b) == reverse.combine(b, a)