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PlcInterp.sml
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PlcInterp.sml
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exception Impossible
exception HDEmptySeq
exception TLEmptySeq
exception ValueNotFoundInMatch
exception NotAFunc
(* fun getV(v:plcVal) =
case v of IntV(a) => a
| BoolV(a) => a
| _ => raise Impossible *)
fun getV(n:plcVal) =
case n of IntV(a) => a
| _ => raise Impossible
fun getBoolV(v:plcVal) =
case v of BoolV(a) => a
| _ => raise Impossible
fun eval (e:expr,env:((string * plcVal) list)) =
(case e of
ConI n => IntV(n)
| ConB b => BoolV(b)
| Var x =>
let val v = (lookup env x)
in v
end
| If(exp1,v1,v2) =>
let val eExp1 = eval(exp1,env)
in
if (getBoolV(eExp1))
then eval(v1,env)
else eval(v2,env)
end
| Let(var, value, pg) =>
let val evar = eval(value,env)
in eval(pg,(var,evar)::env)
end
| ESeq(t) => SeqV([])
| List([]) => ListV([])
| List(l) =>
if (List.length l) > 1
then ListV((List.map (fn (x) => eval (x,env)) l))
else raise Impossible
| Prim1(ope,expr) =>
if ope = "!" then
let val eExp = eval(expr,env)
in BoolV(not (getBoolV(eExp)))
end
else if ope = "-" then
let val eExp = eval(expr,env)
in IntV(~(getV(eExp)))
end
else if ope = "tl" then
let
val eExpr = (eval (expr,env))
in
case eExpr of
SeqV([]) => raise TLEmptySeq
| SeqV(l) => SeqV(tl(l))
| _ => raise Impossible
end
else if ope = "hd" then
let val eExpr = (eval (expr,env))
in
case eExpr of
SeqV([]) => raise HDEmptySeq
| SeqV(l) => hd(l)
| _ => raise Impossible
end
else if ope = "print" then
let val eExpr = (eval (expr,env))
in
print(val2string(eExpr)^"\n");
ListV([])
end
else if ope = "ise" then
let
val eExpr = (eval (expr,env))
in
case eExpr of
SeqV(l) => BoolV(List.null l)
| _ => raise Impossible
end
else raise Impossible
| Prim2(ope,expr1,expr2) =>
(
if ope = "=" orelse ope = "!=" then
let
val eExp1 = (eval (expr1,env))
val eExp2 = (eval (expr2,env))
in
if ope = "!="
then BoolV(not (eExp1 = eExp2))
else BoolV(eExp1 = eExp2)
end
else if ope = "+" orelse ope = "-" orelse ope = "*" orelse ope = "/" then
let
val eExp1 = (eval (expr1,env))
val eExp2 = (eval (expr2,env))
in
if ope = "+" then IntV(getV(eExp1)+getV(eExp2))
else if ope = "-" then IntV(getV(eExp1)-getV(eExp2))
else if ope = "*" then IntV(getV(eExp1)*getV(eExp2))
else if ope = "/" then IntV(getV(eExp1) div getV(eExp2))
else raise Impossible
end
else if ope = "<" orelse ope = "<=" then
let
val eExp1 = (eval (expr1,env))
val eExp2 = (eval (expr2,env))
in
if ope = "<"
then BoolV(getV(eExp1) < getV(eExp2))
else BoolV(getV(eExp1) <= getV(eExp2))
end
else if ope = "&&" then
let
val eExp1 = (eval (expr1,env))
val eExp2 = (eval (expr2,env))
in BoolV(getBoolV(eExp1) andalso getBoolV(eExp2))
end
else if ope = "::" then
let
val eExp1 = (eval (expr1,env))
val eExp2 = (eval (expr2,env))
in
case eExp1 of SeqV(a) =>
(case eExp2 of SeqV(b) =>
SeqV(a@b)
| _ => SeqV(eExp2::a)
)
| _ => (case eExp2 of SeqV([]) =>
SeqV(eExp1::[])
| SeqV(b) => SeqV(eExp1::b)
)
end
else if ope = ";" then
let
val eExp1 = (eval (expr1,env))
val eExp2 = (eval (expr2,env))
in eExp2
end
else raise Impossible
)
| Item(n,expr) =>
let val eExpr = eval (expr,env)
in
case eExpr of
ListV(l) => List.nth (l, n-1)
| _ => raise Impossible
end
| Match(expComp, lOp) =>
let
val eExprComp = eval(expComp,env)
val validOpt = List.filter (fn((opt,ret)) =>
case opt of
SOME(tp) => (eval (tp,env)) = eExprComp
| NONE => true
) lOp
in
if(List.null validOpt)
then raise ValueNotFoundInMatch
else eval(#2((List.nth (validOpt, 0))),env)
end
| Letrec(name, tps, l, tret, b, pg) => eval(pg,(name,Clos(name,l,b,env))::env)
| Call(f,pr) =>
let
val vf = eval(f,env);
val prEv = eval(pr,env);
in
case vf of
(Clos("", l, b, envP)) =>
let val NewEnv = (l, prEv)::envP
in eval(b,NewEnv)
end
| (Clos(f, l, b, envP)) =>
let val NewEnv = (l, prEv)::(f,vf)::envP
in eval(b,NewEnv)
end
| _ => raise NotAFunc
end
| Anon(tps, l, b) => Clos("",l, b, env)
)