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|
(*
* Translation from one sort to another
*)
functor MDLAstTranslation
(structure AstPP : MDL_AST_PRETTY_PRINTER
structure AstRewriter : MDL_AST_REWRITER
sharing AstRewriter.Ast = AstPP.Ast
) : MDL_AST_TRANSLATION =
struct
structure Ast = AstPP.Ast
structure A = Ast
structure R = AstRewriter
structure H = HashTable
fun error msg = MLRiscErrorMsg.error("MDLAstTranslation",msg)
type 'a map = {origName : Ast.id,
newName : Ast.id,
ty : Ast.ty
} -> 'a
type 'a folder = {origName : Ast.id,
newName : Ast.id,
ty : Ast.ty} * 'a -> 'a
fun ID x = A.IDexp(A.IDENT([],x))
exception NoName
(*
* Treat a type expression as a pattern and compute its set of
* variable bindings. Duplicates are given unique suffixes.
*)
fun bindingsInTy ty =
let val namesTable = H.mkTable (HashString.hashString,op =)(32,NoName)
val variables = ref 0
fun enterName id =
let val _ = variables := !variables + 1
val (_, totalCount) = H.lookup namesTable id
in totalCount := !totalCount + 1
end handle _ => H.insert namesTable (id, (ref 0,ref 1))
fun enter(A.IDty(A.IDENT(_,id))) = enterName id
| enter(A.TYVARty(A.VARtv id)) = enterName id
| enter(A.APPty(A.IDENT(_,id),_)) = enterName id
| enter(A.CELLty id) = enterName id
| enter(A.TUPLEty tys) = app enter tys
| enter(A.RECORDty ltys) = app (fn (id, _) => enterName id) ltys
| enter t = error("bindingsInTy: "^PP.text(AstPP.ty t))
val stripTicks = String.map (fn #"'" => #"t" | c => c)
fun getName id =
let val (currentCount, totalCount) = H.lookup namesTable id
in stripTicks(
if !totalCount = 1 then id (* use the same name *)
else
(currentCount := !currentCount + 1;
id^Int.toString(!currentCount)
)
)
end
in enter ty;
(!variables, getName)
end
(*
* Translate a type into a pattern expression
*)
fun mapTyToPat f' ty =
let val (_,getName) = bindingsInTy ty
fun f(id,ty) = f'{origName=id,newName=getName id,ty=ty}
fun g(A.IDty(A.IDENT(_,id)), ty) = f(id,ty)
| g(A.TYVARty(A.VARtv id), ty) = f(id, ty)
| g(A.APPty(A.IDENT(_,id),_), ty) = f(id, ty)
| g(A.CELLty id, ty) = f(id, ty)
| g(A.TUPLEty tys, _) = A.TUPLEpat(map g' tys)
| g(A.RECORDty ltys, _) = A.RECORDpat(map h ltys,false)
| g(t, _) = error("tyToPat: "^PP.text(AstPP.ty t))
and g' t = g(t,t)
and h(lab, ty) = (lab, f(lab, ty))
in g' ty
end
fun foldTy f' x ty =
let val (_,getName) = bindingsInTy ty
fun f(id,ty,x) = f'({origName=id,newName=getName id,ty=ty},x)
fun g(A.IDty(A.IDENT(_,id)),ty,x) = f(id,ty,x)
| g(A.TYVARty(A.VARtv id), ty, x) = f(id,ty,x)
| g(A.APPty(A.IDENT(_,id),_), ty, x) = f(id,ty, x)
| g(A.CELLty id,ty,x) = f(id,ty,x)
| g(A.TUPLEty tys,ty,x) = foldr g' x (rev tys)
| g(A.RECORDty ltys,ty,x) = foldr h x (rev ltys)
| g(t, ty, x) = error("foldTyBindings: "^PP.text(AstPP.ty t))
and g'(t,x) = g(t,t,x)
and h((lab, ty),x) = f(lab,ty,x)
in g'(ty,x)
end
fun foldCons f x (A.CONSbind{ty=NONE, ...}) = x
| foldCons f x (A.CONSbind{ty=SOME ty, ...}) = foldTy f x ty
(*
* Translate a type into an expression
*)
fun mapTyToExp f' ty =
let val (_,getName) = bindingsInTy ty
fun f(id,ty) = f'{origName=id,newName=getName id,ty=ty}
fun g(A.IDty(A.IDENT(_,id)), ty) = f(id, ty)
| g(A.TYVARty(A.VARtv id), ty) = f(id, ty)
| g(A.APPty(A.IDENT(_,id),_), ty) = f(id, ty)
| g(A.CELLty id, ty) = f(id, ty)
| g(A.TUPLEty tys, ty) = A.TUPLEexp(map g' tys)
| g(A.RECORDty ltys, ty) = A.RECORDexp(map h ltys)
| g(t, _) = error("tyToPat: "^PP.text(AstPP.ty t))
and g' t = g(t,t)
and h(lab, ty) = (lab, f(lab, ty))
in g' ty
end
(*
* Translate a constructor into a pattern
*)
fun mapConsToPat {prefix, id} (A.CONSbind{id=x, ty, ...}) =
A.CONSpat(A.IDENT(prefix,x), Option.map (mapTyToPat id) ty)
(*
* Translate a constructor into an expression
*)
fun mapConsToExp {prefix,id} (A.CONSbind{id=x, ty, ...}) =
A.CONSexp(A.IDENT(prefix,x), Option.map (mapTyToExp id) ty)
fun mapConsArgToExp id (A.CONSbind{ty=NONE, ...}) = A.TUPLEexp []
| mapConsArgToExp id (A.CONSbind{ty=SOME ty, ...}) = mapTyToExp id ty
fun mapConsToClause {prefix, pat, exp} cons =
A.CLAUSE([pat(mapConsToPat
{prefix=prefix, id=fn {newName,...} => A.IDpat newName}
cons)],
NONE,
exp)
fun consBindings cons =
let fun enter({newName,origName,ty},bindings) = (newName, ty)::bindings
val bindings = foldCons enter [] cons
fun lookup(id : Ast.id) =
let fun find((b as (x,t))::bs) = if x = id then (ID x,t) else find bs
| find [] = raise NoName
in find bindings end
in lookup
end
(* Simplification *)
local
val NIL = R.noRewrite
fun hasBindings ps =
let val bindings = ref false
fun pat _ (p as A.IDpat x) = (bindings := true; p)
| pat _ p = p
in app (fn p =>
(#pat(R.rewrite{pat=pat,decl=NIL,sexp=NIL,exp=NIL,ty=NIL}) p;
())) ps;
!bindings
end
fun allTheSame [] = true
| allTheSame (x::xs) = List.all (fn x' => x = x') xs
exception Don'tApply
fun reduceExp ==> (exp as A.CASEexp(e,[])) = exp
| reduceExp ==> (A.SEQexp es) =
(A.SEQexp(foldr (fn (A.TUPLEexp [],es) => es
| (A.SEQexp [],es) => es
| (e,es) => e::es
) [] es))
| reduceExp ==>
(exp as A.CASEexp(e,allCs as (c as A.CLAUSE(p1,NONE,e1))::cs)) =
let fun collect(A.CLAUSE([p],NONE,e),Ps) =
let fun ins [] = [([p],e)]
| ins((ps,e')::Ps) =
if e = e' then (p::ps,e)::Ps
else (ps,e')::ins Ps
in ins Ps end
val Ps = foldr collect [] (c::cs)
fun orPat [p] = p
| orPat ps =
if List.all (fn A.WILDpat => true | _ => false) ps then
A.WILDpat
else A.ORpat ps
fun tuplepat [p] = p
| tuplepat ps = A.TUPLEpat ps
fun join([p],e) = A.CLAUSE([p],NONE,e)
| join(ps,e) =
let val xs = map (fn A.TUPLEpat(p::ps) => (p,ps)
| _ => raise Don'tApply) ps
val firstPats = map #1 xs
val restPats = map #2 xs
in if allTheSame (map tuplepat restPats) then
A.CLAUSE([tuplepat(orPat firstPats::hd restPats)],
NONE,e)
else raise Don'tApply
end handle Dont'Apply => A.CLAUSE([orPat ps],NONE,e)
val cs = map join (rev Ps)
in case cs of
[A.CLAUSE([A.TUPLEpat []],NONE,body)] => body
| [A.CLAUSE([_],NONE,body as A.LISTexp([],NONE))] => body
| [A.CLAUSE([A.TUPLEpat(ps)],NONE,body)] =>
if hasBindings ps then
let fun elimOr(pat as A.ORpat p) =
if hasBindings p then pat else A.WILDpat
| elimOr pat = pat
in A.CASEexp(e,
[A.CLAUSE([A.TUPLEpat(map elimOr ps)],NONE,body)])
end
else body
| [A.CLAUSE(ps,NONE,body)] =>
if hasBindings ps then A.CASEexp(e,cs) else body
| _ => A.CASEexp(e,cs)
end
| reduceExp ==> (exp as A.IFexp(a,b,c)) = if b = c then b else exp
| reduceExp ==> e = e
val simplifier =
R.rewrite{pat=NIL,decl=NIL,exp=reduceExp,sexp=NIL,ty=NIL}
in
val simplifyExp = #exp simplifier
val simplifyDecl = #decl simplifier
val simplifyPat = #pat simplifier
val simplifySexp = #sexp simplifier
val simplifyTy = #ty simplifier
fun stripMarks d =
let fun decl ==> (A.MARKdecl(_,d)) = d
| decl ==> d = d
in #decl (R.rewrite{pat=NIL,decl=decl,sexp=NIL,exp=NIL,ty=NIL}) d end
end
end
|
