F#: Reducing an array of numbers as strings to a single integer

Question

I've got an array of strings, call it a, where each individual string represents a number. I also have a function f : int -> int -> int, which I want to use to "reduce a to a single number". I would like to write:

a |> Array.reduce (fun x y -> f (int32 x) (int32 y))

but this does not work, because the type of "reduce" forbids me from returning integers from f (since a is an array of strings)

Is there a functional way to make this work without having to return a string from f or casting the string array to an int array beforehand?

Answer 1

using Array.reduce mapping first

If you don't want to adapt your f to handle strings, and you want to use Array.reduce then yeah I guess you should convert first (and to be honest: it seems easier than doing it manually with your wrapper-lambda) - so why not just use

a
|> Array.map int32
|> Array.reduce f

instead?

if you are concerned with the overhead of producing an intermediate Array you can always switch Array. with Seq. to to it lazily:

a |> Seq.map int32 |> Seq.reduce f

---

using Array.fold

aside from that you can always fold to your hearts desire:

a |> Array.fold (fun n s -> n + int32 s) 0

so you might call this more functional or not ;)