ocaml/camlp4/etc/parserify.ml

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(* camlp4r q_MLast.cmo *)
(* $Id$ *)
value loc = (0, 0);
type spc =
[ SPCterm of (MLast.patt * option MLast.expr)
| SPCnterm of MLast.patt and MLast.expr
| SPCsterm of MLast.patt ]
;
exception NotImpl;
value rec subst v e =
match e with
[ <:expr< $lid:x$ >> -> if x = "strm__" then <:expr< $lid:v$ >> else e
| <:expr< $uid:_$ >> -> e
| <:expr< $int:_$ >> -> e
| <:expr< $chr:_$ >> -> e
| <:expr< $str:_$ >> -> e
| <:expr< $e1$ . $lab$ >> -> <:expr< $subst v e1$ . $lab$ >>
| <:expr< $x$ $y$ >> -> <:expr< $subst v x$ $subst v y$ >>
| <:expr< let $lid:s1$ = $e1$ in $e2$ >> ->
if s1 = v then <:expr< let $lid:s1$ = $subst v e1$ in $e2$ >>
else <:expr< let $lid:s1$ = $subst v e1$ in $subst v e2$ >>
| <:expr< let _ = $e1$ in $e2$ >> ->
<:expr< let _ = $subst v e1$ in $subst v e2$ >>
| <:expr< ($list:el$) >> -> <:expr< ($list:List.map (subst v) el$) >>
| _ -> raise NotImpl ]
;
value rec is_free v =
fun
[ <:expr< $lid:x$ >> -> x <> v
| <:expr< $uid:_$ >> -> True
| <:expr< $int:_$ >> -> True
| <:expr< $chr:_$ >> -> True
| <:expr< $str:_$ >> -> True
| <:expr< $e$ . $_$ >> -> is_free v e
| <:expr< $x$ $y$ >> -> is_free v x && is_free v y
| <:expr< let $lid:s1$ = $e1$ in $e2$ >> ->
is_free v e1 && (s1 = v || is_free v e2)
| <:expr< let _ = $e1$ in $e2$ >> -> is_free v e1 && is_free v e2
| <:expr< ($list:el$) >> -> List.for_all (is_free v) el
| _ -> raise NotImpl ]
;
value gensym =
let cnt = ref 0 in
fun () ->
do { incr cnt; "pr_rp_symb_" ^ string_of_int cnt.val }
;
value free_var_in_expr c e =
let rec loop_alpha v =
let x = String.make 1 v in
if is_free x e then Some x
else if v = 'z' then None
else loop_alpha (Char.chr (Char.code v + 1))
in
let rec loop_count cnt =
let x = String.make 1 c ^ string_of_int cnt in
if is_free x e then x else loop_count (succ cnt)
in
try
match loop_alpha c with
[ Some v -> v
| None -> loop_count 1 ]
with
[ NotImpl -> gensym () ]
;
value parserify =
fun
[ <:expr< $e$ strm__ >> -> e
| e -> <:expr< fun strm__ -> $e$ >> ]
;
value is_raise_failure =
fun
[ <:expr< raise Stream.Failure >> -> True
| _ -> False ]
;
value is_raise_error =
fun
[ <:expr< raise (Stream.Error $_$) >> -> True
| _ -> False ]
;
value semantic e =
try
if is_free "strm__" e then e
else
let v = free_var_in_expr 's' e in
<:expr< let $lid:v$ = strm__ in $subst v e$ >>
with
[ NotImpl -> e ]
;
value rewrite_parser =
rewrite True where rec rewrite top ge =
match ge with
[ <:expr< let $p$ = try $e$ with [ Stream.Failure -> raise $exc$ ] in
$sp_kont$ >> ->
let f = parserify e in
<:expr<
match try Some ($f$ strm__) with [ Stream.Failure -> None ] with
[ Some $p$ -> $rewrite False sp_kont$
| _ -> raise $exc$ ]
>>
| <:expr< let $p$ = Stream.count strm__ in $f$ >> ->
try
if is_free "strm__" f then ge
else
let v = free_var_in_expr 's' f in
<:expr<
let $lid:v$ = strm__ in
let $p$ = Stream.count strm__ in $subst v f$
>>
with
[ NotImpl -> ge ]
| <:expr< let $p$ = strm__ in $e$ >> ->
<:expr< let $p$ = strm__ in $rewrite False e$ >>
| <:expr< let $p$ = $f$ strm__ in $sp_kont$ >> when top ->
<:expr<
match try Some ($f$ strm__) with [ Stream.Failure -> None ] with
[ Some $p$ -> $rewrite False sp_kont$
| _ -> raise Stream.Failure ]
>>
| <:expr< let $p$ = $e$ in $sp_kont$ >> ->
if match e with
[ <:expr< match try Some $_$ with [ Stream.Failure -> None ] with
[ $list:_$ ] >>
| <:expr< match Stream.peek strm__ with [ $list:_$ ] >>
| <:expr< try $_$ with [ Stream.Failure -> $_$ ] >>
| <:expr< let $_$ = Stream.count strm__ in $_$ >> -> True
| _ -> False ]
then
let f = rewrite True <:expr< fun strm__ -> $e$ >> in
let exc =
if top then <:expr< Stream.Failure >>
else <:expr< Stream.Error "" >>
in
<:expr<
match try Some ($f$ strm__) with [ Stream.Failure -> None ] with
[ Some $p$ -> $rewrite False sp_kont$
| _ -> raise $exc$ ]
>>
else semantic ge
| <:expr< match try Some $e$ with [ Stream.Failure -> None ] with
[ Some $p$ -> $sp_kont$
| _ -> $p_kont$ ] >> ->
let f = parserify e in
if not top && is_raise_failure p_kont then semantic ge
else
let (p, f, sp_kont, p_kont) =
if top || is_raise_error p_kont then
(p, f, rewrite False sp_kont, rewrite top p_kont)
else
let f =
<:expr<
fun strm__ ->
match
try Some ($f$ strm__) with [ Stream.Failure -> None ]
with
[ Some $p$ -> $rewrite False sp_kont$
| _ -> $rewrite top p_kont$ ]
>>
in
(<:patt< a >>, f, <:expr< a >>,
<:expr< raise (Stream.Error "") >>)
in
<:expr<
match try Some ($f$ strm__) with [ Stream.Failure -> None ] with
[ Some $p$ -> $sp_kont$
| _ -> $p_kont$ ]
>>
| <:expr< match Stream.peek strm__ with [ $list:pel$ ] >> ->
let rec iter pel =
match pel with
[ [(<:patt< Some $p$ >>, eo,
<:expr< do { Stream.junk strm__; $sp_kont$ } >>);
(<:patt< _ >>, None, p_kont) :: _] ->
<:expr<
match Stream.peek strm__ with
[ Some $p$ $when:eo$ ->
do { Stream.junk strm__; $rewrite False sp_kont$ }
| _ -> $rewrite top p_kont$ ]
>>
| [(<:patt< Some $p$ >>, eo,
<:expr< do { Stream.junk strm__; $sp_kont$ } >>) :: pel] ->
let p_kont = iter pel in
<:expr<
match Stream.peek strm__ with
[ Some $p$ $when:eo$ ->
do { Stream.junk strm__; $rewrite False sp_kont$ }
| _ -> $p_kont$ ]
>>
| _ ->
<:expr< match Stream.peek strm__ with [ $list:pel$ ] >> ]
in
iter pel
| <:expr< try Some $e$ with [ Stream.Failure -> $p_kont$ ] >> ->
let f = parserify e in
let e =
<:expr<
match try Some ($f$ strm__) with [ Stream.Failure -> None ] with
[ Some a -> Some a
| _ -> $p_kont$ ]
>>
in
rewrite top e
| <:expr< try $e$ with [ Stream.Failure -> $p_kont$ ] >> ->
let f = parserify e in
let e =
<:expr<
match try Some ($f$ strm__) with [ Stream.Failure -> None ] with
[ Some a -> a
| _ -> $rewrite top p_kont$ ]
>>
in
rewrite top e
| <:expr< $f$ strm__ >> ->
if top then
<:expr<
match try Some ($f$ strm__) with [ Stream.Failure -> None ] with
[ Some a -> a
| _ -> raise Stream.Failure ]
>>
else
let v = free_var_in_expr 's' f in
<:expr< let $lid:v$ = strm__ in $subst v f$ $lid:v$ >>
| e -> semantic e ]
;
value spc_of_parser =
let rec parser_cases e =
match e with
[ <:expr<
match try Some ($f$ strm__) with [ Stream.Failure -> None ] with
[ Some $p$ -> $sp_kont$
| _ -> $p_kont$ ]
>> ->
let spc = (SPCnterm p f, None) in
let (sp, epo, e) = kont sp_kont in
[([spc :: sp], epo, e) :: parser_cases p_kont]
| <:expr<
match Stream.peek strm__ with
[ Some $p$ $when:wo$ -> do { Stream.junk strm__; $sp_kont$ }
| _ -> $p_kont$ ]
>> ->
let spc = (SPCterm (p, wo), None) in
let (sp, epo, e) = kont sp_kont in
[([spc :: sp], epo, e) :: parser_cases p_kont]
| <:expr< let $p$ = strm__ in $sp_kont$ >> ->
let spc = (SPCsterm p, None) in
let (sp, epo, e) = kont sp_kont in
[([spc :: sp], epo, e)]
| <:expr< let $p$ = Stream.count strm__ in $e$ >> -> [([], Some p, e)]
| <:expr< raise Stream.Failure >> -> []
| _ -> [([], None, e)] ]
and kont e =
match e with
[ <:expr<
match try Some ($f$ strm__) with [ Stream.Failure -> None ] with
[ Some $p$ -> $sp_kont$
| _ -> raise (Stream.Error $err$) ]
>> ->
let err =
match err with
[ <:expr< "" >> -> None
| _ -> Some err ]
in
let spc = (SPCnterm p f, err) in
let (sp, epo, e) = kont sp_kont in
([spc :: sp], epo, e)
| <:expr<
match Stream.peek strm__ with
[ Some $p$ $when:wo$ -> do { Stream.junk strm__; $sp_kont$ }
| _ -> raise (Stream.Error $err$) ]
>> ->
let err =
match err with
[ <:expr< "" >> -> None
| _ -> Some err ]
in
let spc = (SPCterm (p, wo), err) in
let (sp, epo, e) = kont sp_kont in
([spc :: sp], epo, e)
| <:expr< let $p$ = strm__ in $sp_kont$ >> ->
let spc = (SPCsterm p, None) in
let (sp, epo, e) = kont sp_kont in
([spc :: sp], epo, e)
| <:expr< let $p$ = Stream.count strm__ in $e$ >> -> ([], Some p, e)
| _ -> ([], None, e) ]
in
parser_cases
;
value parser_of_expr e = spc_of_parser (rewrite_parser e);