Question

Probably a silly question, but I just got started with F# and I’ve got a little problem.

Say I have a function like this:

let multiplyByTwo x = x * 2

When I call this like this:

let result = multiplyByTwo 5

Everything is alright, the result is 10.

When I call it like this:

let result = multiplyByTwo 2.5

I expect to get 5 or 5.0 as a result. The actual result however is this:

let result = multiplyByTwo 2.5;;
———————————^^^

stdin(4,28): error FS0001: This expression was expected to have type

int     

but here has type

float

Because I want this function to be somewhat generic (i.e. accept both floating point numbers and integers), I don’t like this. My question of course: how does one solve this?

Answer 1

let inline mulBy2 x = (float x) * 2.0

let a = mulBy2 3 // 6.0 : float
let b = mulBy2 2.5 // 5.0 : float
let c = mulBy2 "4" // 8.0 : float