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|
open Ast
exception FoundRedex of expr index
let check_redex (ast : expr ast) (i : expr index) : unit =
match get_subexpr ast i with
| App (f, _) -> (
match get_subexpr ast f with
| Lam (_, _) -> raise (FoundRedex i)
| _ -> ())
| Int _ -> ()
| Lam (_, _) -> ()
| Prim (Add, (l, r)) | Prim (Sub, (l, r)) | Prim (Mul, (l, r)) -> (
match (get_subexpr ast l, get_subexpr ast r) with
| Int _, Int _ -> raise (FoundRedex i)
| _ -> ())
| Var _ -> ()
let find_redex_cbv_in (ast : expr ast) : expr index -> unit =
let rec loop (i : expr index) : unit =
(match get_subexpr ast i with
| App (f, x) ->
loop f;
loop x
| Int _ -> ()
| Lam (_, _) -> ()
| Prim (Add, (l, r)) | Prim (Sub, (l, r)) | Prim (Mul, (l, r)) ->
loop l;
loop r
| Var _ -> ());
check_redex ast i
in
loop
let find_redex_cbn_in (ast : expr ast) : expr index -> unit =
let rec loop (i : expr index) : unit =
check_redex ast i;
match get_subexpr ast i with
| App (f, x) ->
loop f;
loop x
| Int _ -> ()
| Lam (_, _) -> ()
| Prim (Add, (l, r)) | Prim (Sub, (l, r)) | Prim (Mul, (l, r)) ->
loop l;
loop r
| Var _ -> ()
in
loop
let find_redex_cbv (ast : expr ast) : expr index option =
try
find_redex_cbv_in ast ast.root;
None
with FoundRedex i -> Some i
let find_redex_cbn (ast : expr ast) : expr index option =
try
find_redex_cbn_in ast ast.root;
None
with FoundRedex i -> Some i
exception NotARedex of expr ast
let reduce (ast : expr ast) (i : expr index) : expr ast =
let fail () = raise (NotARedex { ast with root = i }) in
let ast = copy ast in
let must_int j = match get_subexpr ast j with Int n -> n | _ -> fail () in
Arraylist.set ast.subexprs i.index
(match get_subexpr ast i with
| App (_f, _x) -> failwith "TODO"
| Prim (Add, (l, r)) -> Int (must_int l + must_int r)
| Prim (Sub, (l, r)) -> Int (must_int l - must_int r)
| Prim (Mul, (l, r)) -> Int (must_int l * must_int r)
| _ -> fail ());
ast
|
