How make tail recursion in scala from Future.foreach call back?

Question

Consider a scala code:

def myRecursiveFunction(id:string):Unit= {
    myAsyncDao.search(id).foreach {response=>
        myRecursiveFunction(response.id)
    }
}
//myAsyncDao.search returns a Future
//response have id field for further computations

If I put @tailrec on top op function, compile complains Recusive call not in tail position.

Can it be optimizated as tail recursion?

As you can read [in this answer](http://stackoverflow.com/a/16986416/2522681) your solution does not require tail recursion because the stack does not grow anyway. — Michael Lang, Jun 24 '15 at 07:02

digit plumber · Answer 1 · 2015-06-24T07:27:55.923

0

How about

def myRecursiveFunction(id:string):Future[Unit]= {
    myAsyncDao.search(id) flatMap {response=>
        myRecursiveFunction(response.id)
    }
}

Update:

def search(id: Future[Int]) = Future { 5 }

@tailrec
def myRecursiveFunction(id: Future[Int]):Future[Unit]= {
    val response = search(id)
    myRecursiveFunction(response)    
}

edited Jun 24 '15 at 07:27

answered Jun 24 '15 at 06:41

digit plumber

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Did you even try it before posting ? It does not work still the same error. – curious Jun 24 '15 at 07:06
With the exception that the OP's `search` function does not take a `Future[Int]` but instead a `String` which makes the situation more complex, unfortunately. – Michael Lang Jun 24 '15 at 08:11

How make tail recursion in scala from Future.foreach call back?

1 Answers1