53 lines
1.6 KiB
OCaml
53 lines
1.6 KiB
OCaml
type var = int
|
|
|
|
type t =
|
|
| Var of var
|
|
| Const of string
|
|
| Free of string
|
|
| Function of string * t list
|
|
|
|
type match_result = AllSubst of t | SomeSubst of t | NoneSubst | MatchErr
|
|
|
|
let merge_result m1 m2 =
|
|
match (m1, m2) with
|
|
| AllSubst t1, AllSubst t2 -> if t1 = t2 then AllSubst t1 else MatchErr
|
|
| AllSubst t1, SomeSubst _ -> SomeSubst t1
|
|
| SomeSubst _, AllSubst t2 -> SomeSubst t2
|
|
| SomeSubst t1, SomeSubst t2 -> if t1 = t2 then SomeSubst t1 else MatchErr
|
|
| NoneSubst, _ -> m2
|
|
| _, NoneSubst -> m1
|
|
| _ -> MatchErr
|
|
|
|
let rec match_term x t1 t2 =
|
|
if x = t1 then if t1 = t2 then SomeSubst t2 else AllSubst t2
|
|
else
|
|
match (t1, t2) with
|
|
| Var v1, Var v2 -> if v1 = v2 then NoneSubst else MatchErr
|
|
| Const s1, Const s2 -> if s1 = s2 then NoneSubst else MatchErr
|
|
| Free s1, Free s2 -> if s1 = s2 then NoneSubst else MatchErr
|
|
| Function (f1, ts1), Function (f2, ts2) ->
|
|
if f1 = f2 && List.(length ts1 = length ts2) then
|
|
List.(map2 (match_term x) ts1 ts2 |> fold_left merge_result NoneSubst)
|
|
else MatchErr
|
|
| _ -> MatchErr
|
|
|
|
let rec inc_var = function
|
|
| Var v -> Var (v + 1)
|
|
| Const s -> Const s
|
|
| Free s -> Free s
|
|
| Function (f, ts) -> Function (f, List.map inc_var ts)
|
|
|
|
let rec occurs t = function
|
|
| Function (_, ts) -> List.exists (occurs t) ts
|
|
| s -> t = s
|
|
|
|
let to_string binders =
|
|
let open Format in
|
|
let rec aux = function
|
|
| Var v -> List.nth binders v
|
|
| Const c -> c
|
|
| Free f -> f
|
|
| Function (f, args) ->
|
|
sprintf "%s(%s)" f (String.concat ", " (List.map aux args))
|
|
in
|
|
aux
|