Recursive function not returning Int

Question

I have a recursive function that will repeat the function until the if condition is not met then output an integer. However the function outside this function that requires an integer is receiving a unit. How should I modify the code in order to return an int?

count(r,c,1,0)

   def count(r: Int, c: Int, countR: Int, lalaCount: Int): Int = {
    if (countR < (r + 1)) count(r,c,countR + 1, lalaCount + countR)
    else (lalaCount + c + 1)
   }

This is the whole program

object hw1 {
  def pascal(c: Int, r: Int): Int = {

   count(r,c,1,0)

   def count(r: Int, c: Int, countR: Int, lalaCount: Int): Int = {
    if (countR < (r + 1)) count(r,c,countR + 1, lalaCount + countR)
    else (lalaCount + c + 1)
   }
  } //On this line eclipse is saying "Multiple markers at this line
    //- type mismatch;  found   : Unit  required: Int
    //- type mismatch;  found   : Unit  required: Int
pascal(3,4)

}

What makes you think it is receiving a Unit? Your function is defined as returning an Int, so you're definitely getting an Int back, how did you determine that you're getting Unit back? — adelbertc
– adelbertc, Commented Sep 30, 2012 at 4:43
You should consider to accept some answers if they help to resolve your problems — Oleg Pavliv
– Oleg Pavliv, Commented Sep 30, 2012 at 6:08
Please do not violate the Honor code principles you agreed. This is a homework assignment coming from Functional Programming Principles in Scala online course. — Tomasz Nurkiewicz
– Tomasz Nurkiewicz, Commented Sep 30, 2012 at 8:10

DaoWen · Accepted Answer · 2012-09-30 05:50:54Z

6

The value returned from pascal is the last expression it contains. You want it to be your evaluation of count but that's not the last thing. Assignments (def, val etc) are of type Unit, as you've discovered:

  def pascal(c: Int, r: Int): Int = {

   count(r,c,1,0) // => Int

   def count(r: Int, c: Int, countR: Int, lalaCount: Int): Int = {
    if (countR < (r + 1)) count(r,c,countR + 1, lalaCount + countR)
    else (lalaCount + c + 1)
   } // => Unit
  }

Just move count(r,c,1,0) after the def and that should fix the problem.

edited Sep 30, 2012 at 5:50

DaoWen

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answered Sep 30, 2012 at 5:18

Luigi Plinge

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2 Comments

user1656125 Over a year ago

So pascal looks at count(r,c,1,0) first and says this is a unit instead of realizing that it calls a local function that returns an int?

DaoWen Over a year ago

Luigi was saying that the def inside the function actually gets evaluated and returns Unit. I've edited the answer to make that a little bit more clear.

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