Higher-Order Functions with Tuples

Question

I have the following problem. I was trying to make a high-order function that accepts two parameters: the String and the function type. Function type is defined this way: ``` (String, List[String]) => List[(String, List[String])] ``` I have also defined two functions `f1` and `f2` that has the same type. Afterwards I am trying to call `myfun` with `f1` or `f2`. Here is the code: ``` object Main extends App { def f1(t: (String,List[String])): List[(String,List[String])] = ... def f2(t: (String,List[String])): List[(String,List[String])] = ... def myfun(tableName: String)(fn: (String,List[String]) => List[(String,List[String])]): List[(String,List[String])] = ... val res: List[(String,List[String])] = myfun("...")(f1) res foreach println val res2: List[(String,List[String])] = myfun("...")(f2) res2 foreach println } ``` and here is the error: ``` [error] found : (String, List[String]) => List[(String, List[String])] [error] required: (String, List[String]) => List[(String, List[String])…

Accepted Answer

Try this. Note the extra set of parenthesis surrounding the argument list to `fn`.

```
def myfun(tableName: String)
         (fn: ((String,List[String])) => List[(String,List[String])]):  List[(String,List[String])] = ...
```

Unfortunately this extra set of parenthesis is needed to distinguish

```
Function1[(String, List[String]), List[(String,List[String])]] 
```

from

```
Function2[String, List[String], List[(String, List[String])]]
```

Higher-Order Functions with Tuples

Solution

Problem