Scala Best Practices - Avoid using reduce

Some collections are empty, and reduce deals with them by throwing an exception:

Seq.empty[Int].reduce(_ + _)
// java.lang.UnsupportedOperationException: empty.reduceLeft
// 	at scala.collection.LinearSeqOptimized.reduceLeft(LinearSeqOptimized.scala:139)
// 	at scala.collection.LinearSeqOptimized.reduceLeft$(LinearSeqOptimized.scala:138)
// 	at scala.collection.immutable.List.reduceLeft(List.scala:89)
// 	at scala.collection.TraversableOnce.reduce(TraversableOnce.scala:211)
// 	at scala.collection.TraversableOnce.reduce$(TraversableOnce.scala:211)
// 	at scala.collection.AbstractTraversable.reduce(Traversable.scala:108)
// 	at repl.Session$App$$anonfun$1.apply$mcI$sp(traversable_reduce.md:9)
// 	at repl.Session$App$$anonfun$1.apply(traversable_reduce.md:9)
// 	at repl.Session$App$$anonfun$1.apply(traversable_reduce.md:9)

reduceOption is a safer alternative, since it encodes the possibility of the empty list in its return type:

Seq(1, 2, 3).reduceOption(_ + _)
// res0: Option[Int] = Some(6)

Seq.empty[Int].reduceOption(_ + _)
// res1: Option[Int] = None

Avoid using reduce

Reason

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