What is Scala's yield?

Question

I understand Ruby and Python\'s yield. What does Scala\'s yield do?

Answer 1

yield is more flexible than map(), see example below

val aList = List( 1,2,3,4,5 )

val res3 = for ( al <- aList if al > 3 ) yield al + 1 
val res4 = aList.map( _+ 1 > 3 ) 

println( res3 )
println( res4 )

yield will print result like: List(5, 6), which is good

while map() will return result like: List(false, false, true, true, true), which probably is not what you intend.