elm/exercises/triangle/Triangle.example.elm

module Triangle exposing (..)

import Set


type Triangle
    = Equilateral
    | Isosceles
    | Scalene


version : Int
version =
    2


triangleKind : comparable -> comparable -> comparable -> Result String Triangle
triangleKind x y z =
    if x <= 0 || y <= 0 || z <= 0 then
        Err "Invalid lengths"
    else if x + y <= z || x + z <= y || y + z <= x then
        Err "Violates inequality"
    else
        case Set.size (Set.fromList [ x, y, z ]) of
            1 ->
                Ok Equilateral

            2 ->
                Ok Isosceles

            _ ->
                Ok Scalene