What is Scala's yield?

Question

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

Answer 1

Yes, as Earwicker said, it's pretty much the equivalent to LINQ's select and has very little to do with Ruby's and Python's yield. Basically, where in C# you would write

from ... select ??? 

in Scala you have instead

for ... yield ???

It's also important to understand that for-comprehensions don't just work with sequences, but with any type which defines certain methods, just like LINQ:

• If your type defines just map, it allows for-expressions consisting of a single generator.
• If it defines flatMap as well as map, it allows for-expressions consisting of several generators.
• If it defines foreach, it allows for-loops without yield (both with single and multiple generators).
• If it defines filter, it allows for-filter expressions starting with an if in the for expression.