Question

I get data from a 3rd party API that just gives me back a System.Object, which I know to be a double[] under the covers. And to deal with that return type, I have found the code below to work wonderfully. However, I also get back some int[] arrays that are also masquerading as System.Object, specifically dates in the form YYYYMMDD (e.g. 20100310).

The conversion to float fails, and it just says that the specified cast is not valid. Does anyone out there know how to make this work for integers?

let oIsNull (obj : System.Object) = obj = null
let oIsArray (obj : System.Object) = obj.GetType().IsArray

let o2f (obj : System.Object) = 
    let mutable arr = [|Double.NaN|]
    if (oIsNull obj = false) && (oIsArray obj = true) then
        let objArr = obj :?> obj[]
        let u = objArr.GetUpperBound(0)
        let floatArr : float[] = Array.zeroCreate (u  + 1);
        for i in 0..u do 
            if objArr.[i] = null then
                floatArr.[i] <- Double.NaN
            else 
                let t = objArr.[i].GetType() 
                floatArr.[i] <- objArr.[i] :?> float 
            //else floatArr.[i] <- float objArr.[i]
        arr <- floatArr
    arr

Answer 1

Do you mean that you want

floatArr.[i] <- float (objArr.[i] :?> int)

to do the object cast to int then promote to float?

Actually you would be better served by using pattern matching on types along the lines

open System

let o2f (obj : System.Object) =
  match obj with
  | :? array<float> as arr -> arr
  | :? array<int> as irr -> irr |> Array.map float 
  | _ -> [|Double.NaN|]