ocaml variant types manipulations

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);;

(Let us know if this is homework so we don't give away too much stuff you're supposed to figure out.) — Jeffrey Scofield
Thanks Jeffrey. This is not directly out of my homework, although an answer to this question will help me towards solving a question. I would really appreciate an answer on how +. operator works, and how InFloat (float i1 +. f2) is a valid expression. (ref pad's answer) — Gitmo
@Gitmo: You edited example is wrong; it supposes to be let var = InFloat(float 2 +. 3.2). Regarding (+.) operators on float, Jeffrey's comment on my answer is a great explanation. — pad
By the way, semi-colons aren't necessary except in the ocaml REPL (to tell it when to stop!). — Asherah

pad pad · Accepted Answer · 2012-02-04T21:07:31

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)

ocaml variant types manipulations

2 Answers