Re-organized a lot of code, changed functions so that functions capture the surrounding environment and execute in that environment
This commit is contained in:
20
lib/ast.ml
20
lib/ast.ml
@@ -11,32 +11,36 @@ type lisp_val =
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generally, builtin functions should handle their arguments directly,
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and eval forms in the environment as necessary. *)
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| LBuiltinFunction of string * (environment -> lisp_val -> lisp_val)
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(* a function is a name, a parameter list, and function body. *)
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| LFunction of string * lisp_val * lisp_val
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(* a function is a name, captured environment, a parameter list, and function body. *)
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| LFunction of string * environment * lisp_val * lisp_val
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(* a macro is exactly the same as a function, with the distinction
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that it receives all of its arguments completely unevaluated
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in a compiled lisp this would probably make more of a difference *)
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| LMacro of string * lisp_val * lisp_val
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| LMacro of string * environment * lisp_val * lisp_val
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| LQuoted of lisp_val
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and environment = (string, lisp_val) Hashtbl.t list
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let env_add env s v =
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let env_set_local env s v =
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match env with
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| [] -> ()
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| e1 :: _ -> Hashtbl.add e1 s v
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| e1 :: _ -> Hashtbl.replace e1 s v
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let env_new_lexical env =
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let h = Hashtbl.create 16 in
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h :: env
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let rec env_root env =
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let rec env_root (env : environment) =
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match env with
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| [] -> raise (Invalid_argument "Empty environment passed to env_root!")
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| e :: [] -> e
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| _ :: t -> env_root t
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let env_set_global env s v =
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Hashtbl.replace (env_root env) s v
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let env_copy env =
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List.map Hashtbl.copy env
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let rec dbg_print_one v =
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let pf = Printf.sprintf in
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@@ -48,9 +52,9 @@ let rec dbg_print_one v =
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| LCons (a, b) -> pf "(%s . %s)" (dbg_print_one a) (dbg_print_one b)
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| LDouble d -> pf "<double: %f>" d
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| LBuiltinFunction (name, _) -> pf "<builtin: %s>" name
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| LFunction (name, args, _) -> pf "<function: '%s' lambda-list: %s>"
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| LFunction (name, _, args, _) -> pf "<function: '%s' lambda-list: %s>"
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name (dbg_print_one args)
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| LMacro (name, args, _) -> pf "<function '%s' lambda-list: %s>"
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| LMacro (name, _, args, _) -> pf "<function '%s' lambda-list: %s>"
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name (dbg_print_one args)
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| LQuoted v -> pf "<quote: %s>" (dbg_print_one v)
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(*| _ -> "<Something else>"*)
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73
lib/eval.ml
73
lib/eval.ml
@@ -5,7 +5,7 @@ open InterpreterStdlib;;
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let default_env: environment = [Hashtbl.create 1024];;
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let add_builtin s f =
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env_add default_env s (LBuiltinFunction (s, f))
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env_set_global default_env s (LBuiltinFunction (s, f))
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let () = add_builtin "+" iadd
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let () = add_builtin "-" isub
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let () = add_builtin "car" car
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@@ -24,18 +24,11 @@ let rec eval_sym (env: environment) (s: string) =
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| None -> eval_sym rest s
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| Some v -> v
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let rec eval_one env v =
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match v with
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| LInt x -> LInt x
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| LDouble x -> LDouble x
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| LString s -> LString s
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let rec eval_one env = function
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| LSymbol s -> eval_sym env s
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| LNil -> LNil
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| LCons (func, args) -> eval_call env func args
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| LBuiltinFunction (n, f) -> LBuiltinFunction (n, f)
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| LFunction (n, l, f) -> LFunction (n, l, f)
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| LMacro (n, l, f) -> LMacro (n, l, f)
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| LCons (func, args) -> eval_call env (eval_one env func) args
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| LQuoted v -> v
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| v -> v (* All other forms are self-evaluating *)
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(* Evaluate a list of values, without evaluating the resulting
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function or macro call. Since macros and functions inherently
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@@ -50,44 +43,44 @@ and eval_body env body =
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match body with
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| LNil -> LNil
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| LCons (form, LNil) -> eval_one env form
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| LCons (form, next) ->
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ignore (eval_one env form); eval_body env next
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| LCons (form, next) -> ignore (eval_one env form); eval_body env next
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| _ -> LNil
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and eval_apply env func args =
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let lexical_env = env_new_lexical env in
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let rec bind_one s a =
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match a with
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| LNil -> raise (Invalid_argument "not enough arguments supplied to function")
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| LCons (value, resta) ->
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env_add lexical_env s value; resta
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| _ -> raise (Invalid_argument "invalid argument list")
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and bind_args l a =
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match l with
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| LNil -> (match a with
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| LNil -> ()
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| _ -> raise (Invalid_argument "too many arguments supplied to function"))
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| LCons (LSymbol sym, LSymbol restl)->
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env_add lexical_env restl (bind_one sym a)
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| LCons (LSymbol sym, restl) ->
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bind_args restl (bind_one sym a)
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| _ -> raise (Invalid_argument "Failure while binding arguments")
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in match func with
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| LFunction (_, l, b) ->
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bind_args l args;
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and err s = raise (Invalid_argument s)
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and bind_args env = function
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| LNil -> (function
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| LNil -> () | _ -> err "bind_args")
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| LCons (LSymbol hl, tl) -> (function
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| LCons (ha, ta) ->
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env_set_local env hl ha;
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bind_args env tl ta;
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| _ -> err "bind_args")
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| _ -> fun _ -> err "bind_args"
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and eval_apply args = function
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| LFunction (_, e, l, b) ->
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let lexical_env = env_new_lexical e in
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bind_args lexical_env l args;
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eval_body lexical_env b
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| LMacro (_, l, b) ->
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bind_args l args;
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| LMacro (_, e, l, b) ->
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let lexical_env = env_new_lexical e in
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bind_args lexical_env l args;
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eval_body lexical_env b
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| _ -> LNil
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| v ->
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err ("Non-macro non-function value passed to eval_apply "
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^ dbg_print_one v); LNil
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and eval_call env func args =
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match eval_one env func with
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match func with
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| LBuiltinFunction (_, f) -> f env (eval_list env args)
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| LFunction (n, l, b) -> eval_apply env (LFunction (n, l, b)) (eval_list env args)
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| LMacro (n, l, b) -> eval_apply env (LMacro (n, l, b)) args
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(* The function calls don't happen in the calling environment,
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so it makes no sense to pass env to a call. *)
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| LFunction _ -> eval_apply (eval_list env args) func
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(* Macros are the same, they just return code that *will* be evaluated
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in the calling environment *)
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| LMacro _ -> eval_apply args func
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| v -> raise (Invalid_argument
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(Printf.sprintf "eval_apply: cannot call non-function object %s" (dbg_print_one v)));;
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@@ -51,11 +51,10 @@ a new function.
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(bind-function 'sym '(a b) '(+ a b))
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*)
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let bind_function env vs =
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let root = [env_root env] in
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let rais () = raise (Invalid_argument "not enough args to bind-function") in
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match vs with
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| LCons (LSymbol sym, LCons (ll, body)) ->
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let f = (LFunction (sym, ll, body)) in
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env_add root sym f; f
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let f = (LFunction (sym, env_copy env, ll, body)) in
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env_set_global env sym f;
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f
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| _ -> rais ()
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