CODEWITHSUNDEEP
swiftswift-protocols
Josh Paradroid
Josh Paradroid

Reputation: 1414

Extending Collection of FloatingPoint

I'm trying to extend a Collection of FloatingPoint-conforming elements to work out an average.

extension Collection where Element: FloatingPoint {
    func sum() -> Element {
        return reduce(0, +)
    }

    func average() -> Element {
        return sum() / Int(count)
    }
}

sum() works fine but average() has an error.

Binary operator '/' cannot be applied to operands of type 'Self.Element' and 'Int'

I'm not sure why this is. Self.Element is a FloatingPoint. I would expect to be able to divide this.

(I'm also aware that there's a divide-by-zero issue, but I'll fix that later.)

Upvotes: 0

Views: 64

Answers (1)

Sandeep
Sandeep

Reputation: 21154

You average didnt work because you were trying to divide some FloatingPoint type with integer. Use Element(count) to create new element of same type to divide.

  extension Collection where Element: FloatingPoint {
      func sum() -> Element {
        return reduce(0, +)
      }

      func average() -> Element {
        guard !isEmpty else { return 0 }
        return sum() / Element(count)
      }
    }

And this works because FloatingPoint protocol declares following initializer,

public init(_ value: Int)

This works with Swift 4.1, since count is Int. For earlier versions of Swift use,

  extension Collection where Element: FloatingPoint {
      func sum() -> Element {
        return reduce(0, +)
      }

      func average() -> Element {
        guard !isEmpty else { return 0 }
        return sum() / Element(Int(count))
      }

  }

Upvotes: 3

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