Cool thanks, didn't realize it was due to implicits. Here are my tests, for the record. Works in Scala: for {a <- Seq(Some(1), None, Some(3)); b <- a} yie

Cool thanks, didn't realize it was due to implicits. Here are my tests, for the record. Works in Scala: for {a <- Seq(Some(1), None, Some(3)); b <- a} yield b Doesn't work in Haskell: do a <- [Just 1, Nothing, Just 3]; b <- a; return b