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|
(* interp.sml
*
* COPYRIGHT (c) 1992 AT&T Bell Laboratories
*)
structure Interp =
struct
local
val exit = OS.Process.exit
fun ordof(s, i) = Char.ord(String.sub(s, i))
exception NotAChar
exception NotAReal
fun fromStr x =
(case Char.fromString x
of SOME c => c
| NONE => raise NotAChar)
fun strToReal s =
(case Real.fromString s
of SOME r => r
| _ => raise NotAReal)
fun intToReal x =
(strToReal ((Int.toString x) ^ ".0"))
val explode = (fn x => map Char.toString (explode x))
val implode = (fn x => implode (map fromStr x))
open Objects
val dict = ref ([] : {key : string, value : object} list)
fun dictInsert (NAME key, value) = let
fun find [] = [{key=key, value=value}]
| find (x::r) = if (key = #key x)
then {key=key, value=value}::r
else x :: (find r)
in
dict := find(!dict)
end
| dictInsert _ = raise Fail "dictInsert"
fun prObj outStrm obj = let
fun printf args = TextIO.output(outStrm, implode args)
fun pr (NUMBER n) = printf[" ", Real.toString n, "\n"]
| pr (NAME s) = printf[" ", s, "\n"]
| pr (LITERAL s) = printf[" ", s, "\n"]
| pr (LIST l) = app pr l
| pr MARK = printf[" MARK\n"]
| pr (OPERATOR _) = printf[" <operator>\n"]
| pr TOP = printf[" TOP OF STACK\n"]
| pr _ = printf[" <object>\n"]
in
pr obj
end
in
exception Stop
fun error opName stk = let
fun prStk ([], _) = ()
| prStk (_, 0) = ()
| prStk (obj::r, i) = (prObj TextIO.stdErr obj; prStk(r, i-1))
in
TextIO.output(TextIO.stdErr, "ERROR: "^opName^"\n");
prStk (stk, 10);
raise (Fail opName)
end
fun installOperator (name, rator) =
dictInsert (NAME name, OPERATOR rator)
fun ps_def (v::k::r) = (dictInsert(k, v); r)
| ps_def stk = error "ps_def" stk
local
fun binOp (f, opName) = let
fun g ((NUMBER arg1)::(NUMBER arg2)::r) =
NUMBER(f(arg2, arg1)) :: r
| g stk = error opName stk
in
g
end
in
val ps_add = binOp (op +, "add")
val ps_sub = binOp (op -, "sub")
val ps_mul = binOp (op *, "mul")
val ps_div = binOp (op /, "div")
end
fun ps_rand stk = (NUMBER 0.5)::stk (** ??? **)
fun ps_print (obj::r) = (prObj TextIO.stdOut obj; r)
| ps_print stk = error "print" stk
fun ps_dup (obj::r) = (obj::obj::r)
| ps_dup stk = error "dup" stk
fun ps_stop _ = raise Stop
(* initialize dictionary and begin parsing input *)
fun parse inStrm = let
fun getc () = case TextIO.input1 inStrm of NONE => ""
| SOME c => Char.toString c
fun peek () = case TextIO.lookahead inStrm
of SOME x => Char.toString x
| _ => ""
(* parse one token from inStrm *)
fun toke deferred = let
fun doChar "" = exit OS.Process.success
| doChar "%" = let
fun lp "\n" = doChar(getc())
| lp "" = exit OS.Process.success
| lp _ = lp(getc())
in
lp(getc())
end
| doChar "{" = (MARK, deferred+1)
| doChar "}" = (UNMARK, deferred-1)
| doChar c = if Char.isSpace (fromStr c)
then doChar(getc())
else let
fun lp buf = (case peek()
of "{" => buf
| "}" => buf
| "%" => buf
| c => if Char.isSpace(fromStr c)
then buf
else (getc(); lp(c::buf))
(* end case *))
val tok = implode (rev (lp [c]))
val hd = ordof(tok, 0)
in
if (hd = ord (#"/"))
then (LITERAL(substring(tok, 1, size tok - 1)), deferred)
else
if ((Char.isDigit (chr hd)) orelse (hd = ord (#"-")))
then (NUMBER(strToReal(tok)), deferred)
else (NAME tok, deferred)
end
in
doChar(getc())
end
(* execute a token (if not deferred) *)
fun exec (UNMARK, stk, _) = let
fun lp ([], _) = raise Fail "MARK"
| lp (MARK::r, l) = (LIST l)::r
| lp (x::r, l) = lp (r, x::l)
in
lp (stk, [])
end
| exec (OPERATOR f, stk, 0) = f stk
| exec (LIST l, stk, 0) = let
fun execBody ([], stk) = stk
| execBody (obj::r, stk) = (exec(obj, stk, 0); execBody(r, stk))
in
execBody (l, stk)
end
| exec (NAME s, stk, 0) = let
fun find [] = raise Fail "undefined name"
| find ({key, value}::r) = if (key = s) then value else find r
in
exec (find (!dict), stk, 0)
end
| exec (obj, stk, _) = obj::stk
fun lp (stk, level) = let
val (obj, level) = toke level
val stk = exec (obj, stk, level)
in
lp (stk, level)
end
in
installOperator ("add", ps_add);
installOperator ("def", ps_def);
installOperator ("div", ps_div);
installOperator ("dup", ps_dup);
installOperator ("mul", ps_mul);
installOperator ("print", ps_print);
installOperator ("rand", ps_rand);
installOperator ("stop", ps_stop);
installOperator ("sub", ps_sub);
(lp ([], 0)) handle Stop => ()
end (* parse *)
end (* local *)
end (* Interp *)
|
