b2t2 table encoding

table.ml

(* table *)
type 'a header = (string * 'a) list
type 'a header = string list

class ['a] table (header : 'b header)  = object
  val mutable header : 'b header = header
  val mutable columns : 'a list = []
  method columns : 'a list = columns
  
  (* add rows, can't enforce the header *)
  method add_rows (rows : 'a list) : 'a list =
    columns <- rows @ columns;
    columns
    
  end;;

(* empty table - weak type *)
let empty_table = new table [];;

(* example encoding - students *)
class student (n : string) (a : int) (c: string) =
object
    val mutable name : string option = Some n
    val mutable age : int option  = Some a
    val mutable favourite_colour : string option = Some c

    method name : string option = name
    method set_name : string option -> unit = fun new_name -> name <- new_name

    method age : int option = age
    method set_age : int option -> unit = fun new_age -> age <- new_age

    method favourite_colour : string option = favourite_colour
    method set_favourite_colour : string option -> unit = fun new_colour -> favourite_colour <- new_colour
    
end;;

let bob = new student "Bob" 12 "Blue";; 
let alice = new student "Alice" 17 "Green";; 
let eve = new student "Eve" 13 "Red";; 

let students = new table ["name"; "age"; "favourite_colour"];;
students#add_rows [bob; alice; eve];;

table encoding in ocaml that meets the b2t2 specification but is too restrictive to type well-meaning programs.

example students table from b2t2 specification