Is there default parameter in F#?

Question

I wrote a program to convert file size from bytes to a human readable format in F#:

let rec sizeFmt num i =
    let suffix="B"
    let unit = ["";"Ki";"Mi";"Gi";"Ti";"Pi";"Ei";"Zi"]
    match abs num with
        | x when x < 1024.0 -> printfn "%3.1f %s%s" num unit.[i] suffix
        | _ -> sizeFmt (num / 1024.0) (i+1)

let humanReadable n =
    sizeFmt (float n) 0   

Run example:

> humanReadable 33;;
33.0 B
val it : unit = ()
> humanReadable 323379443;;
308.4 MiB
val it : unit = ()
> 

Question:

1. It would be nice if I can set i=0 as the default value in the sizeFmt funciton. I checked the F# documentation, only found that there's no default parameter. So I have to write a wrapper function humanReadable. Is there a better way?

2. In order to handle both int and float type input like humanReadable 123;; and humanReadable 123433.33;;, I have to add a float n in the wrapper function. The obvious problem is: it is very easy to exceed the max int size which is 2,147,483,647. I guess there might be a better way, are there?

Answer 1

If sizeFmt is only used by humanReadable, it makes sense to make it an inner function. That avoids the 'parameter default' issue.

Also, marking the outer function inline causes it to accept any type of n that supports explicit conversion to float.

let inline humanReadable n =
    let rec sizeFmt num i =
        let suffix="B"
        let unit = ["";"Ki";"Mi";"Gi";"Ti";"Pi";"Ei";"Zi"]
        match abs num with
            | x when x < 1024.0 -> printfn "%3.1f %s%s" num unit.[i] suffix
            | _ -> sizeFmt (num / 1024.0) (i+1)
    sizeFmt (float n) 0   

humanReadable 123 //works
humanReadable 123433.33 //also works