Scala Program that can only be executed using map function and not for yield construct?

Question
1

I am trying to figure out a program that can only be done with map function and not for - yield function. I did figure out a program that can only done using for yield and it can’t be just done using map alone, it requires map and filter.

for {
  i <- 1 until n
  j <- 1 until i
  if isPrime(i + j)
} yield (i, j)

This is an example i found out from an online course. Similarly i am trying to figure out an example where it can be only run using map function and not for yield construct.

2

There isn’t one, period.

foo.map(f) can always be written like for { i <- foo } yield f(i) since the latter is just sugar syntax for the former.

3

Without for, this is equivalent to

(1 until n).flatMap { i =>
  (1 until i).filter(j => isPrime(i + j)).map(j => (i, j))
}

As Luis said, you can’t write it with just map.