Question

I have a variant type like this:

type score = 
    InInteger of int
    | InFloat of float ;;

Now, given two scores (InInteger(5) and InFloat(5.5)), I want to add, subtract them etc..

How can this be done?

PS – I’m a newbie to OCaml.

Edit::

More specifically:

How does this work?

let n = InInt(2);;
let m = InFloat(3.2);;

let var = InFloat(float n +.  m);;

Answer 1

First, discriminated unions require their identifiers starting with upper cases:

type score = 
    InInteger of int
    | InFloat of float

Second, you can define an add function on this datatype by pattern matching all possible cases and returning appropriate values:

let add s1 s2 = 
    match s1, s2 with
    | InInteger i1, InInteger i2 -> InInteger (i1 + i2)
    | InInteger i1, InFloat f2   -> InFloat (float i1 +. f2)
    | InFloat f1, InInteger i2   -> InFloat (f1 +. float i2)
    | InFloat f1, InFloat f2     -> InFloat (f1 +. f2)