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step A scaffolding
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Fabian
Joel Martin
parent
4cb61f5426
commit
6b14be1285
@ -1,4 +1,4 @@
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STEP_BINS = step0_repl step1_read_print step2_eval step3_env step4_if_fn_do step6_file step7_quote step8_macros step9_try
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STEP_BINS = step0_repl step1_read_print step2_eval step3_env step4_if_fn_do step6_file step7_quote step8_macros step9_try stepA_mal
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sml_MODE_DEFAULT = polyml
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sml_MODE_CONFIG = .smlmode
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12
impls/sml/stepA_mal.mlb
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12
impls/sml/stepA_mal.mlb
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local
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$(SML_LIB)/basis/basis.mlb
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util.sml
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types.sml
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printer.sml
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reader.sml
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env.sml
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core.sml
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stepA_mal.sml
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in
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main.sml
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end
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157
impls/sml/stepA_mal.sml
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157
impls/sml/stepA_mal.sml
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fun read s =
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readStr s
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fun eval e ast = eval' e (expandMacro 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)
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| eval' e (MAP m) = MAP (List.map (fn (k, v) => (eval e k, eval e v)) m)
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| eval' e ast = ast
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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 (SYMBOL "quote") = SOME evalQuote
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| specialEval (SYMBOL "quasiquote") = SOME evalQuasiquote
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| specialEval (SYMBOL "quasiquoteexpand") = SOME (fn _ => expandQuasiquote)
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| specialEval (SYMBOL "defmacro!") = SOME evalDefmacro
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| specialEval (SYMBOL "macroexpand") = SOME expandMacro
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| specialEval (SYMBOL "try*") = SOME evalTry
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| specialEval _ = NONE
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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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| evalDef _ _ = raise NotApplicable "def! needs a symbol and a form to evaluate"
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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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and evalDo e (x::xs) = foldl (fn (x, _) => eval e x) (eval e x) xs
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| evalDo _ _ = raise NotApplicable "do needs at least one argument"
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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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| evalIf e [c,a] = evalIf e [c,a,NIL]
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| evalIf _ _ = raise NotApplicable "if needs two or three arguments"
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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)
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and evalQuote e [x] = x
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| evalQuote _ _ = raise NotApplicable "quote needs one argument"
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and evalQuasiquote e args = eval e (expandQuasiquote args)
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and expandQuasiquote [LIST [SYMBOL "unquote", x]] = x
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| expandQuasiquote [LIST l] = LIST (foldr quasiFolder [] l)
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| expandQuasiquote [VECTOR v] = LIST [SYMBOL "vec", LIST (foldr quasiFolder [] v)]
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| expandQuasiquote [m as MAP _] = LIST [SYMBOL "quote", m]
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| expandQuasiquote [s as SYMBOL _] = LIST [SYMBOL "quote", s]
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| expandQuasiquote [x] = x
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| expandQuasiquote _ = raise NotApplicable "quasiquote needs one argument"
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and quasiFolder (LIST [SYMBOL "splice-unquote", x], acc) = [SYMBOL "concat", x, LIST acc]
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| quasiFolder (x, acc) = [SYMBOL "cons", expandQuasiquote [x], LIST acc]
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and evalDefmacro e [SYMBOL s, LIST [SYMBOL "fn*", LIST binds, body]] = let val m = makeMacro e binds body in (def s m e; m) end
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| evalDefmacro e [SYMBOL s, LIST [SYMBOL "fn*", VECTOR binds, body]] = let val m = makeMacro e binds body in (def s m e; m) end
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| evalDefmacro _ _ = raise NotApplicable "defmacro! needs a name, a list of bindings, and a body"
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and makeMacro e binds body = MACRO (fn (exprs) => eval (bind (interleave binds exprs) (inside e)) body)
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and expandMacro e [(ast as LIST (SYMBOL s::args))] = (case lookup e s of SOME (MACRO m) => m args | _ => ast)
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| expandMacro _ [ast] = ast
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| expandMacro _ _ = raise NotApplicable "macroexpand needs one argument"
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and evalTry e [a, LIST [SYMBOL "catch*", b, c]] = (eval e a handle ex => evalCatch (inside e) b ex c)
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| evalTry e [a] = eval e a
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| evalTry _ _ = raise NotApplicable "try* needs a form to evaluate"
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and evalCatch e b ex body = eval (bind [b, exnVal ex] e) body
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and exnVal (MalException x) = x
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| exnVal (NotDefined msg) = STRING msg
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| exnVal (NotApplicable msg) = STRING msg
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| exnVal (OutOfBounds msg) = STRING msg
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| exnVal exn = STRING (exnMessage exn)
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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))
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and evalSymbol e s = valOrElse (lookup e s)
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(fn _ => raise NotDefined ("'" ^ s ^ "' not found"))
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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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and bind' evl (SYMBOL "&"::v::(SYMBOL s)::vs) e = (def s (LIST (map evl (v::vs))) e; e)
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| bind' _ [SYMBOL "&", SYMBOL s] e = (def s (LIST []) e; e)
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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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fun print f =
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prReadableStr f
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fun rep e s =
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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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| MalException e => "ERROR: " ^ (prStr e)
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| e => "ERROR: " ^ (exnMessage e)
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val initEnv = ENV (NS (ref [])) |> bind coreNs
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fun repl e =
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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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let val s = rep e line
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val _ = print(s ^ "\n")
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in
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repl e
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end
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| NONE => ()
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) end
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val prelude = " \
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\\
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\(def! not (fn* (a) (if a false true))) \
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\\
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\(def! \
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\ load-file \
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\ (fn* (f) \
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\ (eval (read-string (str \"(do \" (slurp f) \"\nnil)\")))))\
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\\
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\(defmacro! \
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\ cond \
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\ (fn* (& xs) \
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\ (if (> (count xs) 0) \
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\ (list 'if (first xs) \
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\ (if (> (count xs) 1) \
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\ (nth xs 1) \
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\ (throw \"odd number of forms to cond\")) \
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\ (cons 'cond (rest (rest xs)))))))"
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fun main () = (
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bind [
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SYMBOL "eval",
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FN (fn ([x]) => eval initEnv x
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| _ => raise NotApplicable "'eval' requires one argument")
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] initEnv;
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rep initEnv ("(do " ^ prelude ^ " nil)");
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case CommandLine.arguments () of
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prog::args => (
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def "*ARGV*" (LIST (map STRING args)) initEnv;
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rep initEnv ("(load-file \"" ^ prog ^ "\")");
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()
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)
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| args => (
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def "*ARGV*" (LIST (map STRING args)) initEnv;
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repl initEnv
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)
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)
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