adamc@38: (* Copyright (c) 2008, Adam Chlipala
adamc@38:  * All rights reserved.
adamc@38:  *
adamc@38:  * Redistribution and use in source and binary forms, with or without
adamc@38:  * modification, are permitted provided that the following conditions are met:
adamc@38:  *
adamc@38:  * - Redistributions of source code must retain the above copyright notice,
adamc@38:  *   this list of conditions and the following disclaimer.
adamc@38:  * - Redistributions in binary form must reproduce the above copyright notice,
adamc@38:  *   this list of conditions and the following disclaimer in the documentation
adamc@38:  *   and/or other materials provided with the distribution.
adamc@38:  * - The names of contributors may not be used to endorse or promote products
adamc@38:  *   derived from this software without specific prior written permission.
adamc@38:  *
adamc@38:  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
adamc@38:  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
adamc@38:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
adamc@38:  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
adamc@38:  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
adamc@38:  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
adamc@38:  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
adamc@38:  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
adamc@38:  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
adamc@38:  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
adamc@38:  * POSSIBILITY OF SUCH DAMAGE.
adamc@38:  *)
adamc@38: 
adamc@38: structure ExplUtil :> EXPL_UTIL = struct
adamc@38: 
adamc@38: open Expl
adamc@38: 
adamc@38: structure S = Search
adamc@38: 
adamc@38: structure Kind = struct
adamc@38: 
adamc@38: fun mapfold f =
adamc@38:     let
adamc@38:         fun mfk k acc =
adamc@38:             S.bindP (mfk' k acc, f)
adamc@38: 
adamc@38:         and mfk' (kAll as (k, loc)) =
adamc@38:             case k of
adamc@38:                 KType => S.return2 kAll
adamc@38: 
adamc@38:               | KArrow (k1, k2) =>
adamc@38:                 S.bind2 (mfk k1,
adamc@38:                       fn k1' =>
adamc@38:                          S.map2 (mfk k2,
adamc@38:                               fn k2' =>
adamc@38:                                  (KArrow (k1', k2'), loc)))
adamc@38: 
adamc@38:               | KName => S.return2 kAll
adamc@38: 
adamc@38:               | KRecord k =>
adamc@38:                 S.map2 (mfk k,
adamc@38:                         fn k' =>
adamc@38:                            (KRecord k', loc))
adamc@87: 
adamc@87:               | KUnit => S.return2 kAll
adamc@213: 
adamc@213:               | KTuple ks =>
adamc@213:                 S.map2 (ListUtil.mapfold mfk ks,
adamc@213:                         fn ks' =>
adamc@213:                            (KTuple ks', loc))
adamc@38:     in
adamc@38:         mfk
adamc@38:     end
adamc@38: 
adamc@38: fun exists f k =
adamc@38:     case mapfold (fn k => fn () =>
adamc@38:                              if f k then
adamc@38:                                  S.Return ()
adamc@38:                              else
adamc@38:                                  S.Continue (k, ())) k () of
adamc@38:         S.Return _ => true
adamc@38:       | S.Continue _ => false
adamc@38: 
adamc@38: end
adamc@38: 
adamc@38: structure Con = struct
adamc@38: 
adamc@38: datatype binder =
adamc@38:          Rel of string * Expl.kind
adamc@38:        | Named of string * Expl.kind
adamc@38: 
adamc@38: fun mapfoldB {kind = fk, con = fc, bind} =
adamc@38:     let
adamc@38:         val mfk = Kind.mapfold fk
adamc@38: 
adamc@38:         fun mfc ctx c acc =
adamc@38:             S.bindP (mfc' ctx c acc, fc ctx)
adamc@38: 
adamc@38:         and mfc' ctx (cAll as (c, loc)) =
adamc@38:             case c of
adamc@38:                 TFun (c1, c2) =>
adamc@38:                 S.bind2 (mfc ctx c1,
adamc@38:                       fn c1' =>
adamc@38:                          S.map2 (mfc ctx c2,
adamc@38:                               fn c2' =>
adamc@38:                                  (TFun (c1', c2'), loc)))
adamc@38:               | TCFun (x, k, c) =>
adamc@38:                 S.bind2 (mfk k,
adamc@38:                       fn k' =>
adamc@38:                          S.map2 (mfc (bind (ctx, Rel (x, k))) c,
adamc@38:                               fn c' =>
adamc@38:                                  (TCFun (x, k', c'), loc)))
adamc@38:               | TRecord c =>
adamc@38:                 S.map2 (mfc ctx c,
adamc@38:                         fn c' =>
adamc@38:                            (TRecord c', loc))
adamc@38: 
adamc@38:               | CRel _ => S.return2 cAll
adamc@38:               | CNamed _ => S.return2 cAll
adamc@38:               | CModProj _ => S.return2 cAll
adamc@38:               | CApp (c1, c2) =>
adamc@38:                 S.bind2 (mfc ctx c1,
adamc@38:                       fn c1' =>
adamc@38:                          S.map2 (mfc ctx c2,
adamc@38:                               fn c2' =>
adamc@38:                                  (CApp (c1', c2'), loc)))
adamc@38:               | CAbs (x, k, c) =>
adamc@38:                 S.bind2 (mfk k,
adamc@38:                       fn k' =>
adamc@38:                          S.map2 (mfc (bind (ctx, Rel (x, k))) c,
adamc@38:                               fn c' =>
adamc@38:                                  (CAbs (x, k', c'), loc)))
adamc@38: 
adamc@38:               | CName _ => S.return2 cAll
adamc@38: 
adamc@38:               | CRecord (k, xcs) =>
adamc@38:                 S.bind2 (mfk k,
adamc@38:                       fn k' =>
adamc@38:                          S.map2 (ListUtil.mapfold (fn (x, c) =>
adamc@38:                                                       S.bind2 (mfc ctx x,
adamc@38:                                                             fn x' =>
adamc@38:                                                                S.map2 (mfc ctx c,
adamc@38:                                                                     fn c' =>
adamc@38:                                                                        (x', c'))))
adamc@38:                                  xcs,
adamc@38:                               fn xcs' =>
adamc@38:                                  (CRecord (k', xcs'), loc)))
adamc@38:               | CConcat (c1, c2) =>
adamc@38:                 S.bind2 (mfc ctx c1,
adamc@38:                       fn c1' =>
adamc@38:                          S.map2 (mfc ctx c2,
adamc@38:                               fn c2' =>
adamc@38:                                  (CConcat (c1', c2'), loc)))
adamc@68:               | CFold (k1, k2) =>
adamc@68:                 S.bind2 (mfk k1,
adamc@68:                          fn k1' =>
adamc@68:                             S.map2 (mfk k2,
adamc@68:                                     fn k2' =>
adamc@68:                                        (CFold (k1', k2'), loc)))
adamc@87: 
adamc@87:               | CUnit => S.return2 cAll
adamc@213: 
adamc@213:               | CTuple cs =>
adamc@213:                 S.map2 (ListUtil.mapfold (mfc ctx) cs,
adamc@213:                         fn cs' =>
adamc@213:                            (CTuple cs', loc))
adamc@213: 
adamc@213:               | CProj (c, n) =>
adamc@213:                 S.map2 (mfc ctx c,
adamc@213:                         fn c' =>
adamc@213:                            (CProj (c', n), loc))
adamc@38:     in
adamc@38:         mfc
adamc@38:     end
adamc@38: 
adamc@38: fun mapfold {kind = fk, con = fc} =
adamc@38:     mapfoldB {kind = fk,
adamc@38:               con = fn () => fc,
adamc@38:               bind = fn ((), _) => ()} ()
adamc@38: 
adamc@38: fun mapB {kind, con, bind} ctx c =
adamc@38:     case mapfoldB {kind = fn k => fn () => S.Continue (kind k, ()),
adamc@38:                    con = fn ctx => fn c => fn () => S.Continue (con ctx c, ()),
adamc@38:                    bind = bind} ctx c () of
adamc@38:         S.Continue (c, ()) => c
adamc@38:       | S.Return _ => raise Fail "ExplUtil.Con.mapB: Impossible"
adamc@38: 
adamc@38: fun map {kind, con} s =
adamc@38:     case mapfold {kind = fn k => fn () => S.Continue (kind k, ()),
adamc@38:                   con = fn c => fn () => S.Continue (con c, ())} s () of
adamc@38:         S.Return () => raise Fail "ExplUtil.Con.map: Impossible"
adamc@38:       | S.Continue (s, ()) => s
adamc@38: 
adamc@38: fun exists {kind, con} k =
adamc@38:     case mapfold {kind = fn k => fn () =>
adamc@38:                                     if kind k then
adamc@38:                                         S.Return ()
adamc@38:                                     else
adamc@38:                                         S.Continue (k, ()),
adamc@38:                   con = fn c => fn () =>
adamc@38:                                     if con c then
adamc@38:                                         S.Return ()
adamc@38:                                     else
adamc@38:                                         S.Continue (c, ())} k () of
adamc@38:         S.Return _ => true
adamc@38:       | S.Continue _ => false
adamc@38: 
adamc@38: end
adamc@38: 
adamc@38: structure Exp = struct
adamc@38: 
adamc@38: datatype binder =
adamc@38:          RelC of string * Expl.kind
adamc@38:        | NamedC of string * Expl.kind
adamc@38:        | RelE of string * Expl.con
adamc@38:        | NamedE of string * Expl.con
adamc@38: 
adamc@38: fun mapfoldB {kind = fk, con = fc, exp = fe, bind} =
adamc@38:     let
adamc@38:         val mfk = Kind.mapfold fk
adamc@38: 
adamc@38:         fun bind' (ctx, b) =
adamc@38:             let
adamc@38:                 val b' = case b of
adamc@38:                              Con.Rel x => RelC x
adamc@38:                            | Con.Named x => NamedC x
adamc@38:             in
adamc@38:                 bind (ctx, b')
adamc@38:             end
adamc@38:         val mfc = Con.mapfoldB {kind = fk, con = fc, bind = bind'}
adamc@38: 
adamc@38:         fun mfe ctx e acc =
adamc@38:             S.bindP (mfe' ctx e acc, fe ctx)
adamc@38: 
adamc@38:         and mfe' ctx (eAll as (e, loc)) =
adamc@38:             case e of
adamc@38:                 EPrim _ => S.return2 eAll
adamc@38:               | ERel _ => S.return2 eAll
adamc@38:               | ENamed _ => S.return2 eAll
adamc@38:               | EModProj _ => S.return2 eAll
adamc@38:               | EApp (e1, e2) =>
adamc@38:                 S.bind2 (mfe ctx e1,
adamc@38:                       fn e1' =>
adamc@38:                          S.map2 (mfe ctx e2,
adamc@38:                               fn e2' =>
adamc@38:                                  (EApp (e1', e2'), loc)))
adamc@38:               | EAbs (x, dom, ran, e) =>
adamc@38:                 S.bind2 (mfc ctx dom,
adamc@38:                       fn dom' =>
adamc@38:                          S.bind2 (mfc ctx ran,
adamc@38:                                   fn ran' =>
adamc@38:                                      S.map2 (mfe (bind (ctx, RelE (x, dom'))) e,
adamc@38:                                           fn e' =>
adamc@38:                                              (EAbs (x, dom', ran', e'), loc))))
adamc@38:                          
adamc@38:               | ECApp (e, c) =>
adamc@38:                 S.bind2 (mfe ctx e,
adamc@38:                       fn e' =>
adamc@38:                          S.map2 (mfc ctx c,
adamc@38:                               fn c' =>
adamc@38:                                  (ECApp (e', c'), loc)))
adamc@38:               | ECAbs (x, k, e) =>
adamc@38:                 S.bind2 (mfk k,
adamc@38:                       fn k' =>
adamc@38:                          S.map2 (mfe (bind (ctx, RelC (x, k))) e,
adamc@38:                               fn e' =>
adamc@38:                                  (ECAbs (x, k', e'), loc)))
adamc@38: 
adamc@38:               | ERecord xes =>
adamc@38:                 S.map2 (ListUtil.mapfold (fn (x, e, t) =>
adamc@38:                                              S.bind2 (mfc ctx x,
adamc@38:                                                    fn x' =>
adamc@38:                                                       S.bind2 (mfe ctx e,
adamc@38:                                                            fn e' =>
adamc@38:                                                               S.map2 (mfc ctx t,
adamc@38:                                                                    fn t' =>
adamc@38:                                                                       (x', e', t')))))
adamc@38:                                          xes,
adamc@38:                      fn xes' =>
adamc@38:                         (ERecord xes', loc))
adamc@38:               | EField (e, c, {field, rest}) =>
adamc@38:                 S.bind2 (mfe ctx e,
adamc@38:                       fn e' =>
adamc@38:                          S.bind2 (mfc ctx c,
adamc@38:                               fn c' =>
adamc@38:                                  S.bind2 (mfc ctx field,
adamc@38:                                           fn field' =>
adamc@38:                                              S.map2 (mfc ctx rest,
adamc@38:                                                   fn rest' =>
adamc@38:                                                      (EField (e', c', {field = field', rest = rest'}), loc)))))
adamc@339:               | EWith (e1, c, e2, {field, rest}) =>
adamc@339:                 S.bind2 (mfe ctx e1,
adamc@339:                       fn e1' =>
adamc@339:                          S.bind2 (mfc ctx c,
adamc@339:                               fn c' =>
adamc@339:                                  S.bind2 (mfe ctx e2,
adamc@339:                                        fn e2' =>
adamc@339:                                           S.bind2 (mfc ctx field,
adamc@339:                                                 fn field' =>
adamc@339:                                                    S.map2 (mfc ctx rest,
adamc@339:                                                         fn rest' =>
adamc@339:                                                            (EWith (e1', c', e2', {field = field', rest = rest'}),
adamc@339:                                                             loc))))))
adamc@149:               | ECut (e, c, {field, rest}) =>
adamc@149:                 S.bind2 (mfe ctx e,
adamc@149:                       fn e' =>
adamc@149:                          S.bind2 (mfc ctx c,
adamc@149:                               fn c' =>
adamc@149:                                  S.bind2 (mfc ctx field,
adamc@149:                                           fn field' =>
adamc@149:                                              S.map2 (mfc ctx rest,
adamc@149:                                                   fn rest' =>
adamc@149:                                                      (ECut (e', c', {field = field', rest = rest'}), loc)))))
adamc@72:               | EFold k =>
adamc@72:                 S.map2 (mfk k,
adamc@72:                          fn k' =>
adamc@72:                             (EFold k', loc))
adamc@109: 
adamc@109:               | EWrite e =>
adamc@109:                 S.map2 (mfe ctx e,
adamc@109:                      fn e' =>
adamc@109:                         (EWrite e', loc))
adamc@176: 
adamc@182:               | ECase (e, pes, {disc, result}) =>
adamc@176:                 S.bind2 (mfe ctx e,
adamc@176:                          fn e' =>
adamc@176:                             S.bind2 (ListUtil.mapfold (fn (p, e) =>
adamc@176:                                                          S.map2 (mfe ctx e,
adamc@176:                                                               fn e' => (p, e'))) pes,
adamc@176:                                     fn pes' =>
adamc@182:                                        S.bind2 (mfc ctx disc,
adamc@182:                                                 fn disc' =>
adamc@182:                                                    S.map2 (mfc ctx result,
adamc@182:                                                         fn result' =>
adamc@182:                                                            (ECase (e', pes', {disc = disc', result = result'}), loc)))))
adamc@38:     in
adamc@38:         mfe
adamc@38:     end
adamc@38: 
adamc@38: fun mapfold {kind = fk, con = fc, exp = fe} =
adamc@38:     mapfoldB {kind = fk,
adamc@38:               con = fn () => fc,
adamc@38:               exp = fn () => fe,
adamc@38:               bind = fn ((), _) => ()} ()
adamc@38: 
adamc@38: fun exists {kind, con, exp} k =
adamc@38:     case mapfold {kind = fn k => fn () =>
adamc@38:                                     if kind k then
adamc@38:                                         S.Return ()
adamc@38:                                     else
adamc@38:                                         S.Continue (k, ()),
adamc@38:                   con = fn c => fn () =>
adamc@38:                                     if con c then
adamc@38:                                         S.Return ()
adamc@38:                                     else
adamc@38:                                         S.Continue (c, ()),
adamc@38:                   exp = fn e => fn () =>
adamc@38:                                     if exp e then
adamc@38:                                         S.Return ()
adamc@38:                                     else
adamc@38:                                         S.Continue (e, ())} k () of
adamc@38:         S.Return _ => true
adamc@38:       | S.Continue _ => false
adamc@38: 
adamc@38: end
adamc@38: 
adamc@38: structure Sgn = struct
adamc@38: 
adamc@38: datatype binder =
adamc@38:          RelC of string * Expl.kind
adamc@38:        | NamedC of string * Expl.kind
adamc@38:        | Str of string * Expl.sgn
adamc@64:        | Sgn of string * Expl.sgn
adamc@38: 
adamc@38: fun mapfoldB {kind, con, sgn_item, sgn, bind} =
adamc@38:     let
adamc@38:         fun bind' (ctx, b) =
adamc@38:             let
adamc@38:                 val b' = case b of
adamc@38:                              Con.Rel x => RelC x
adamc@38:                            | Con.Named x => NamedC x
adamc@38:             in
adamc@38:                 bind (ctx, b')
adamc@38:             end
adamc@38:         val con = Con.mapfoldB {kind = kind, con = con, bind = bind'}
adamc@38: 
adamc@38:         val kind = Kind.mapfold kind
adamc@38: 
adamc@38:         fun sgi ctx si acc =
adamc@38:             S.bindP (sgi' ctx si acc, sgn_item ctx)
adamc@38: 
adamc@162:         and sgi' ctx (siAll as (si, loc)) =
adamc@38:             case si of
adamc@38:                 SgiConAbs (x, n, k) =>
adamc@38:                 S.map2 (kind k,
adamc@38:                      fn k' =>
adamc@38:                         (SgiConAbs (x, n, k'), loc))
adamc@38:               | SgiCon (x, n, k, c) =>
adamc@38:                 S.bind2 (kind k,
adamc@38:                      fn k' =>
adamc@38:                         S.map2 (con ctx c,
adamc@38:                              fn c' =>
adamc@38:                                 (SgiCon (x, n, k', c'), loc)))
adamc@191:               | SgiDatatype (x, n, xs, xncs) =>
adamc@162:                 S.map2 (ListUtil.mapfold (fn (x, n, c) =>
adamc@162:                                              case c of
adamc@162:                                                  NONE => S.return2 (x, n, c)
adamc@162:                                                | SOME c =>
adamc@162:                                                  S.map2 (con ctx c,
adamc@162:                                                       fn c' => (x, n, SOME c'))) xncs,
adamc@162:                         fn xncs' =>
adamc@191:                            (SgiDatatype (x, n, xs, xncs'), loc))
adamc@191:               | SgiDatatypeImp (x, n, m1, ms, s, xs, xncs) =>
adamc@162:                 S.map2 (ListUtil.mapfold (fn (x, n, c) =>
adamc@162:                                              case c of
adamc@162:                                                  NONE => S.return2 (x, n, c)
adamc@162:                                                | SOME c =>
adamc@162:                                                  S.map2 (con ctx c,
adamc@162:                                                       fn c' => (x, n, SOME c'))) xncs,
adamc@162:                         fn xncs' =>
adamc@191:                            (SgiDatatypeImp (x, n, m1, ms, s, xs, xncs'), loc))
adamc@38:               | SgiVal (x, n, c) =>
adamc@38:                 S.map2 (con ctx c,
adamc@38:                      fn c' =>
adamc@38:                         (SgiVal (x, n, c'), loc))
adamc@38:               | SgiStr (x, n, s) =>
adamc@38:                 S.map2 (sg ctx s,
adamc@38:                      fn s' =>
adamc@38:                         (SgiStr (x, n, s'), loc))
adamc@64:               | SgiSgn (x, n, s) =>
adamc@64:                 S.map2 (sg ctx s,
adamc@64:                      fn s' =>
adamc@64:                         (SgiSgn (x, n, s'), loc))
adamc@246:               | SgiTable (tn, x, n, c) =>
adamc@246:                 S.map2 (con ctx c,
adamc@246:                         fn c' =>
adamc@246:                            (SgiTable (tn, x, n, c'), loc))
adamc@338:               | SgiSequence _ => S.return2 siAll
adamc@38: 
adamc@38:         and sg ctx s acc =
adamc@38:             S.bindP (sg' ctx s acc, sgn ctx)
adamc@38: 
adamc@38:         and sg' ctx (sAll as (s, loc)) =
adamc@38:             case s of
adamc@38:                 SgnConst sgis =>
adamc@38:                 S.map2 (ListUtil.mapfoldB (fn (ctx, si)  =>
adamc@38:                                               (case #1 si of
adamc@38:                                                    SgiConAbs (x, _, k) =>
adamc@38:                                                    bind (ctx, NamedC (x, k))
adamc@38:                                                  | SgiCon (x, _, k, _) =>
adamc@38:                                                    bind (ctx, NamedC (x, k))
adamc@191:                                                  | SgiDatatype (x, n, _, xncs) =>
adamc@162:                                                    bind (ctx, NamedC (x, (KType, loc)))
adamc@191:                                                  | SgiDatatypeImp (x, _, _, _, _, _, _) =>
adamc@162:                                                    bind (ctx, NamedC (x, (KType, loc)))
adamc@38:                                                  | SgiVal _ => ctx
adamc@38:                                                  | SgiStr (x, _, sgn) =>
adamc@64:                                                    bind (ctx, Str (x, sgn))
adamc@64:                                                  | SgiSgn (x, _, sgn) =>
adamc@246:                                                    bind (ctx, Sgn (x, sgn))
adamc@338:                                                  | SgiTable _ => ctx
adamc@338:                                                  | SgiSequence _ => ctx,
adamc@38:                                                sgi ctx si)) ctx sgis,
adamc@38:                      fn sgis' =>
adamc@38:                         (SgnConst sgis', loc))
adamc@38:                 
adamc@38:               | SgnVar _ => S.return2 sAll
adamc@45: 
adamc@45:               | SgnFun (m, n, s1, s2) =>
adamc@45:                 S.bind2 (sg ctx s1,
adamc@45:                          fn s1' =>
adamc@45:                             S.map2 (sg (bind (ctx, Str (m, s1'))) s2,
adamc@45:                                     fn s2' =>
adamc@45:                                        (SgnFun (m, n, s1', s2'), loc)))
adamc@45:               | SgnWhere (sgn, x, c) =>
adamc@45:                 S.bind2 (sg ctx sgn,
adamc@45:                       fn sgn' =>
adamc@45:                          S.map2 (con ctx c,
adamc@45:                               fn c' =>
adamc@45:                                  (SgnWhere (sgn', x, c'), loc)))
adamc@64:               | SgnProj _ => S.return2 sAll
adamc@38:     in
adamc@38:         sg
adamc@38:     end
adamc@38: 
adamc@38: fun mapfold {kind, con, sgn_item, sgn} =
adamc@38:     mapfoldB {kind = kind,
adamc@38:               con = fn () => con,
adamc@38:               sgn_item = fn () => sgn_item,
adamc@38:               sgn = fn () => sgn,
adamc@38:               bind = fn ((), _) => ()} ()
adamc@38: 
adamc@38: fun map {kind, con, sgn_item, sgn} s =
adamc@38:     case mapfold {kind = fn k => fn () => S.Continue (kind k, ()),
adamc@38:                   con = fn c => fn () => S.Continue (con c, ()),
adamc@38:                   sgn_item = fn si => fn () => S.Continue (sgn_item si, ()),
adamc@38:                   sgn = fn s => fn () => S.Continue (sgn s, ())} s () of
adamc@38:         S.Return () => raise Fail "Expl_util.Sgn.map"
adamc@38:       | S.Continue (s, ()) => s
adamc@38: 
adamc@38: end
adamc@38: 
adamc@38: end