CODEWITHSUNDEEP
scala
Srinivas
Srinivas

Reputation: 2100

Clarification of Scala function

I am trying to execute this function

def sumofdouble[T <:Number] (as:T*): Double = as.foldLeft(0d)(_ + _.doubleValue)

If I try using this function like this, 

sumofdouble(1,2)

I am getting this error

<console>:13: error: inferred type arguments [Int] do not conform to method sumofdouble's type parameter bounds [T <: Number]
sumofdouble(1,2)

Isn't Integer a subtype of Number? Please explain if I am missing something.

Upvotes: 2

Views: 82

Answers (1)

TheMP
TheMP

Reputation: 8427

Looks like you are using java.lang.Number. Unfortunatelly, numeric types in scala do not inherit from this class (for reference look at Int definition - like other scala's numerics it inherits directly from AnyVal - http://www.scala-lang.org/api/2.12.0/scala/Int.html) - it is simply not in their hierarchy. What you want to use is the implicit Numeric type class to convert your numbers.

def foo[T](as: T*)(implicit n: Numeric[T]) = as.foldLeft(0d)(_ + n.toDouble(_))

See this question for further information - Scala equivalent of Java's Number.

Upvotes: 5

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