Algebraic Types

Variant Types (Algebraic Data Types)

OCaml lets you define custom types with type:

type color = Red | Green | Blue

Each variant is a constructor. You match on them:

let color_to_string c =
  match c with
  | Red -> "red"
  | Green -> "green"
  | Blue -> "blue"

Variants with Data

Constructors can carry data:

type shape =
  | Circle of float
  | Rectangle of float * float

Since our transpiler erases types, we will work with simple integer-tagged variants for this lesson.

Your Task

Write a function classify that takes an integer and returns "negative", "zero", or "positive".