CODEWITHSUNDEEP
ocaml
Gitmo
Gitmo

Reputation: 2424

ocaml variant types manipulations

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);;

Upvotes: 2

Views: 355

Answers (2)

pad
pad

Reputation: 41290

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)

Upvotes: 5

Talya
Talya

Reputation: 19367

+. will add floats only, and + will add ints only. That's all there is to it! If you've got floats or ints wrapped inside your union type, you'll have to use match per pad's answer to get them out, then convert the plain numbers within.

Upvotes: 3

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