2021-03-27 13:18:42 +03:00
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fun read s =
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readStr s
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2022-01-10 02:15:40 +03:00
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fun eval e ast = (
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case lookup e "DEBUG-EVAL" of
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SOME(x) => if truthy x
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then TextIO.print ("EVAL: " ^ prReadableStr ast ^ "\n")
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else ()
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| NONE => ();
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eval' e ast)
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and eval' e (LIST (a::args,_)) = (case specialEval a of SOME special => special e args | _ => evalApply e (eval e a) args)
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| eval' e (SYMBOL s) = evalSymbol e s
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| eval' e (VECTOR (v,_)) = VECTOR (map (eval e) v, NO_META)
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| eval' e (MAP (m,_)) = MAP (List.map (fn (k, v) => (k, eval e v)) m, NO_META)
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| eval' e ast = ast
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2021-04-05 18:46:23 +03:00
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and specialEval (SYMBOL "def!") = SOME evalDef
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| specialEval (SYMBOL "let*") = SOME evalLet
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| specialEval (SYMBOL "do") = SOME evalDo
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| specialEval (SYMBOL "if") = SOME evalIf
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| specialEval (SYMBOL "fn*") = SOME evalFn
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| specialEval _ = NONE
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2021-03-27 13:18:42 +03:00
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2021-04-01 19:12:41 +03:00
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and evalDef e [SYMBOL s, ast] = let val v = eval e ast in (def s v e; v) end
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2021-04-06 20:50:25 +03:00
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| evalDef _ _ = raise NotApplicable "def! needs a symbol and a form to evaluate"
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2021-03-27 13:18:42 +03:00
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2021-04-06 20:50:25 +03:00
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and evalLet e [LIST (bs,_), ast] = eval (bindLet bs (inside e)) ast
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| evalLet e [VECTOR (bs,_), ast] = eval (bindLet bs (inside e)) ast
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| evalLet _ _ = raise NotApplicable "let* needs a list of bindings and a form to evaluate"
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2021-03-27 13:18:42 +03:00
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2021-04-01 19:12:41 +03:00
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and evalDo e (x::xs) = foldl (fn (x, _) => eval e x) (eval e x) xs
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2021-04-06 20:50:25 +03:00
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| evalDo _ _ = raise NotApplicable "do needs at least one argument"
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2021-03-27 15:13:42 +03:00
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2021-04-01 19:12:41 +03:00
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and evalIf e [c,a,b] = if truthy (eval e c) then eval e a else eval e b
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2021-03-28 19:39:30 +03:00
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| evalIf e [c,a] = evalIf e [c,a,NIL]
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2021-04-06 20:50:25 +03:00
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| evalIf _ _ = raise NotApplicable "if needs two or three arguments"
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2021-03-27 15:13:42 +03:00
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2021-04-06 20:50:25 +03:00
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and evalFn e [LIST (binds,_),body] = makeFn e binds body
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| evalFn e [VECTOR (binds,_),body] = makeFn e binds body
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| evalFn _ _ = raise NotApplicable "fn* needs a list of bindings and a body"
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and makeFn e binds body = FN (fn (exprs) => eval (bind (interleave binds exprs) (inside e)) body, NO_META)
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2021-03-27 15:13:42 +03:00
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2021-04-06 20:50:25 +03:00
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and evalApply e (FN (f,_)) args = f (map (eval e) args)
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| evalApply _ x args = raise NotApplicable (prStr x ^ " is not applicable on " ^ prStr (LIST (args, NO_META)))
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2021-03-27 13:18:42 +03:00
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and evalSymbol e s = valOrElse (lookup e s)
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(fn _ => raise NotDefined ("symbol '" ^ s ^ "' not found"))
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2021-04-05 20:28:54 +03:00
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and bindLet args e = bind' (eval e) args e
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and bind args e = bind' identity args e
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2021-04-06 20:50:25 +03:00
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and bind' evl (SYMBOL "&"::v::(SYMBOL s)::vs) e = (def s (LIST (map evl (v::vs), NO_META)) e; e)
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| bind' _ [SYMBOL "&", SYMBOL s] e = (def s (LIST ([], NO_META)) e; e)
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2021-04-05 20:28:54 +03:00
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| bind' evl (SYMBOL s::v::rest) e = (def s (evl v) e; bind' evl rest e)
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| bind' _ [] e = e
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| bind' _ _ _ = raise NotApplicable "bindings must be a list of symbol/form pairs"
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2021-03-27 13:18:42 +03:00
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fun print f =
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2021-04-03 00:37:25 +03:00
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prReadableStr f
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2021-03-27 13:18:42 +03:00
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fun rep e s =
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2021-04-01 19:12:41 +03:00
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s |> read |> eval e |> print
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handle Nothing => ""
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| SyntaxError msg => "SYNTAX ERROR: " ^ msg
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| NotApplicable msg => "CANNOT APPLY: " ^ msg
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| NotDefined msg => "NOT DEFINED: " ^ msg
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2021-03-27 13:18:42 +03:00
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2021-04-06 20:50:25 +03:00
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val replEnv = ENV (NS (ref [])) |> bind coreNs
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2021-03-27 13:18:42 +03:00
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2021-03-29 15:06:10 +03:00
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fun repl e =
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2021-03-27 13:18:42 +03:00
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let open TextIO
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in (
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print("user> ");
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case inputLine(stdIn) of
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SOME(line) =>
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2021-04-01 19:12:41 +03:00
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let val s = rep e line
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2021-03-27 13:18:42 +03:00
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val _ = print(s ^ "\n")
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in
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2021-04-01 19:12:41 +03:00
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repl e
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2021-03-27 13:18:42 +03:00
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end
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| NONE => ()
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) end
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2021-03-29 15:06:10 +03:00
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2021-04-03 00:42:35 +03:00
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val prelude = " \
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\(def! not (fn* (a) (if a false true)))"
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fun main () = (
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2021-04-06 20:50:25 +03:00
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rep replEnv ("(do " ^ prelude ^ " nil)");
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repl replEnv
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2021-04-03 00:42:35 +03:00
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)
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