CODEWITHSUNDEEP
scala
blue-sky
blue-sky

Reputation: 53786

How to access function parameter of function parameter?

For below sum method : 

  def sum(term: (Int) => Int , next: (Int) => Int) : Int = {
        0
  }

How can I access the Int parameter of function term

If I try : 

  def sum(term: (param : Int) => Int , next: (Int) => Int) : Int = {
        0
  }

I receive error : 

Multiple markers at this line - only classes can have declared but undefined members - not found: type param - 
 ')' expected but ':' found.

Upvotes: 1

Views: 113

Answers (2)

Ende Neu
Ende Neu

Reputation: 15773

term: (Int) => Int simply tells the compiler that you are passing in a function that takes a a Int parameter and returns another Int, there's no need to bind the variable:

scala> def sum(term: (Int) => Int) : Int = {
 |       term(10)
 |     }
sum: (term: Int => Int)Int

scala> def useSum() = {
 |       sum {
 |         someInt =>
 |           someInt + 1
 |       }
 |     }
useSum: ()Int

scala> useSum
res6: Int = 11

You could also curry the sum function and pass in the parameter you want to apply to the function you are passing:

def sum(someInt: Int)(term: (Int) => Int) : Int = {
  term(someInt)
}

def useSum(someInt: Int) = {
  sum(someInt) {
    someInt =>
      someInt + 1
  }
}

Upvotes: 1

cchantep
cchantep

Reputation: 9158

You can't, as when sum is applied, passed term function is not yet called. BTW there is a syntax error in the second code, as parameters of lambda can't be named in this way.

Upvotes: 0

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