I'm working on this and i'm pretty sure while i was writing it the error din't show up. Now it does and i don't know why and how to solve it, i've searched for long but nothing. it gives Unbound type constructor env on the last line thanks everyone for feedback
module type ENV =
sig
type 't env
val emptyenv : 't -> 't env
val bind : 't env * string * 't -> 't env
val bindlist : 't env * (string list) * ('t list)-> 't env
val applyenv : 't env * string -> 't
exception WrongBindlist
end
module Funenv:ENV =
struct
type 't env = string -> 't
exception WrongBindlist
let emptyenv(x) = function (y: string) -> x
(* x: valore default *)
let applyenv(x,y) = x y
let bind(r, l, e) =
function lu -> if lu = l then e else applyenv(r,lu)
let rec bindlist(r, il, el) = match (il,el) with
| ([],[]) -> r
| i::il1, e::el1 -> bindlist (bind(r, i, e), il1, el1)
| _ -> raise WrongBindlist
end
module Listenv:ENV =
struct
type 't env = (string * 't) list
exception WrongBindlist
let emptyenv(x) = [("", x)]
let rec applyenv(x,y) = match x with
| [(_, e)] -> e
| (i1, e1) :: x1 -> if y = i1 then e1
else applyenv(x1, y)
| [] -> failwith("wrong env")
let bind(r, l, e) = (l, e) :: r
let rec bindlist(r, il, el) = match (il, el) with
| ([],[]) -> r
| i::il1, e::el1 -> bindlist (bind(r, i, e), il1, el1)
| _ -> raise WrongBindlist
end
type ide = string
type exp = Eint of int
| Ebool of bool
type eval = Int of int
| Bool of bool
| Unbound
| Funval of efun
and efun = exp * eval env
Who do you expect
env
to be on this last line?env
is not some type constructor that you have in scope, but a type constructor that belongs to anENV
module.You could make the definition of
exp
andefun
in one of theses modules or useListenv.env
for instance.With the following, it compiles:
Another solution, and that might have been what you were doing, is to put this definition directly in the signature:
But then, you have to provide them again in
Listenv
andFunenv
.