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wip: App_parse in containers_string, a draft of efficient applicative parser combinators

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Simon Cruanes 2015-03-05 01:55:43 +01:00
parent af4bf49156
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@ -85,7 +85,7 @@ Library "containers_iter"
Library "containers_string"
Path: src/string
Pack: true
Modules: KMP, Levenshtein
Modules: KMP, Levenshtein, App_parse
FindlibName: string
FindlibParent: containers

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(*
copyright (c) 2013-2015, simon cruanes
all rights reserved.
redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer. redistributions in binary
form must reproduce the above copyright notice, this list of conditions and the
following disclaimer in the documentation and/or other materials provided with
the distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*)
(** {1 Applicative Parser Combinators} *)
type ('a,'b) result = [`Error of 'b | `Ok of 'a]
type multiplicity =
| Star (* 0 or more *)
| Plus (* 1 or more *)
| Question (* 0 or 1 *)
let str fmt = Printf.sprintf fmt
module CharSet = Set.Make(Char)
module CharMap = Map.Make(Char)
let print_char_set set =
let l = CharSet.fold
(fun c acc -> str "'%c'" c :: acc) set [] in
String.concat ", " l
let domain_of_char_map m =
CharMap.fold (fun c _ set -> CharSet.add c set) m CharSet.empty
let print_char_map map =
let l = CharMap.fold
(fun c _ acc -> str "'%c'" c :: acc) map [] in
String.concat ", " l
(* function composition *)
let compose f g x = f (g x)
let string_of_list l =
let b = Bytes.make (List.length l) ' ' in
List.iteri (fun i c -> Bytes.set b i c) l;
Bytes.unsafe_to_string b
type _ t =
| Return : 'a -> 'a t
| Map : ('a -> 'b) * 'a t -> 'b t
| Filter: ('a -> bool) * 'a t -> 'a t
| App : ('a -> 'b) t * 'a t -> 'b t
| AppLeft : 'a t * 'b t -> 'a t
| AppRight : 'a t * 'b t -> 'b t
| Fail : string -> 'a t
| Int : int t
| Float : float t
| AnyOf : CharSet.t -> char t
| Many : CharSet.t * 'a t * unit t * multiplicity -> 'a list t
| Skip : CharSet.t * 'a t * multiplicity -> unit t (* same as Many, but ignores *)
| SwitchC : 'a t CharMap.t * 'a t option -> 'a t
| SwitchS :'a trie -> 'a t
| Fix : ('a t -> 'a t) -> 'a t
| Eof : unit t
(* a prefix trie *)
and 'a trie =
| TrieEmpty
| TrieNode of 'a t option * 'a trie CharMap.t
let return x = Return x
let success = Return ()
let fail msg = Fail msg
let app f x = App (f, x)
let map f x = match x with
| Map (g, y) -> Map (compose f g, y)
| Return x -> Return (f x)
| _ -> Map (f,x)
let filter f x = Filter (f, x)
let int = Int
let float = Float
let int_first_char =
lazy (CharSet.of_list ['-'; '0'; '1'; '2'; '3'; '4'; '5'; '6'; '7'; '8'; '9'])
(* a set of characters that are valid as first characters of a parser *)
type possible_first_chars =
| Set of CharSet.t
| AllChars
| NoChar
| IsFail of string
(* set of possibilities for the first char of a parser *)
let rec possible_first_chars
: type a. a t -> possible_first_chars
= function
| Return _ -> NoChar
| Map (_, x) -> possible_first_chars x
| Filter (_, x) -> possible_first_chars x
| App (f, _) -> possible_first_chars f
| AppLeft (a, _) -> possible_first_chars a
| AppRight (a, _) -> possible_first_chars a
| Fail e -> IsFail e
| Int -> Set (Lazy.force int_first_char)
| Float -> Set (Lazy.force int_first_char)
| AnyOf set -> Set set
| Many(set, _, _, _) -> Set set
| Skip (set, _, _) -> Set set
| SwitchC (map, None) -> Set (domain_of_char_map map)
| SwitchC (_, Some _) -> AllChars
| SwitchS TrieEmpty -> assert false
| SwitchS (TrieNode (_, m)) -> Set (domain_of_char_map m)
| Fix f ->
let p = f (Fix f) in
possible_first_chars p
| Eof -> NoChar
let many ?(sep=success) t =
match possible_first_chars t with
| Set set -> Many (set, t, sep, Star)
| IsFail msg -> Fail msg
| AllChars -> invalid_arg (str "many: invalid parser (always succeeds)")
| NoChar -> invalid_arg (str "many: invalid parser (does not consume input)")
let many1 ?(sep=success) t =
match possible_first_chars t with
| Set set -> Many (set, t, sep, Plus)
| IsFail msg -> Fail msg
| AllChars -> invalid_arg (str "many: invalid parser (always succeeds)")
| NoChar -> invalid_arg (str "many: invalid parser (does not consume input)")
let skip t =
match possible_first_chars t with
| Set set -> Skip (set, t, Star)
| IsFail msg -> Fail msg
| AllChars -> invalid_arg (str "skip: invalid parser (always succeeds)")
| NoChar -> invalid_arg (str "skip: invalid parser (does not consume input)")
let skip1 t =
match possible_first_chars t with
| Set set -> Skip (set, t, Plus)
| IsFail msg -> Fail msg
| AllChars -> invalid_arg (str "skip: invalid parser (always succeeds)")
| NoChar -> invalid_arg (str "skip: invalid parser (does not consume input)")
let opt t =
match possible_first_chars t with
| Set set ->
map
(function
| [x] -> Some x
| [] -> None
| _ -> assert false
) (Many (set, t, success, Question))
| IsFail msg -> Fail msg
| AllChars -> map (fun x -> Some x) t (* always succeeds *)
| NoChar -> invalid_arg (str "opt: invalid parser (does not consume input)")
let set_of_string s =
let set = ref CharSet.empty in
String.iter
(fun c ->
if CharSet.mem c !set
then invalid_arg (str "any_of: duplicate char %c" c);
set := CharSet.add c !set
) s;
!set
let any_of s = AnyOf (set_of_string s)
let char c = AnyOf (CharSet.singleton c)
let spaces = skip (any_of " \t")
let spaces1 = skip1 (any_of " \t")
let white = skip (any_of " \t\n")
let white1 = skip1 (any_of " \t\n")
let alpha_lower_ = set_of_string "abcdefghijklmonpqrstuvwxyz"
let alpha_upper_ = set_of_string "ABCDEFGHIJKLMONPQRSTUVWXYZ"
let num_ = set_of_string "0123456789"
let alpha_ = CharSet.union alpha_lower_ alpha_upper_
let alpha_lower = AnyOf alpha_lower_
let alpha_upper = AnyOf alpha_upper_
let num = AnyOf num_
let alpha = AnyOf alpha_
let alpha_num = AnyOf (CharSet.union num_ alpha_)
let eof = Eof
let switch_c ?default l =
if l = [] then match default with
| None -> invalid_arg "switch_c: empty list";
| Some d -> d
else
let map = List.fold_left
(fun map (c, t) ->
if CharMap.mem c map
then invalid_arg (str "switch_c: duplicate char %c" c);
CharMap.add c t map
) CharMap.empty l
in
SwitchC (map, default)
exception ExnIsFail of string
let choice l =
if l = [] then invalid_arg "choice: empty list";
(* build a switch by first char *)
try
(* a map and possibly a default parser *)
let map, def = List.fold_left
(fun (map, def) p ->
match possible_first_chars p, def with
| AllChars, Some _ ->
invalid_arg "choice: ambiguous, several parsers accept any input"
| AllChars, None -> map, Some p
| NoChar, _ -> map, def
| IsFail msg, _ -> raise (ExnIsFail msg)
| Set set, def ->
if CharSet.exists (fun c -> CharMap.mem c map) set
then invalid_arg
(str "choice: ambiguous parsers (overlap on {%s})"
(print_char_set (CharSet.inter set (domain_of_char_map map))));
let map = CharSet.fold
(fun c map -> CharMap.add c p map)
set map
in map, def
) (CharMap.empty, None) l
in
SwitchC (map, def)
with ExnIsFail msg ->
fail msg
(* build prefix trie *)
let switch_s l =
if l = [] then invalid_arg "switch_s: empty list";
(* add parser p in trie [t], with key slice of [s] starting at [i] *)
let rec add_trie t s i p =
if i = String.length s
then match t with
| TrieEmpty -> TrieNode (Some p, CharMap.empty)
| TrieNode (Some _, _) -> invalid_arg (str "duplicate key \"%s\"" s)
| TrieNode (None, m) -> TrieNode (Some p, m)
else
let c = String.get s i in
match t with
| TrieEmpty ->
let sub = add_trie TrieEmpty s (i+1) p in
TrieNode (None, CharMap.singleton c sub)
| TrieNode (opt, map) ->
try
let sub = CharMap.find c map in
let sub = add_trie sub s (i+1) p in
TrieNode (opt, CharMap.add c sub map)
with Not_found ->
let sub = add_trie TrieEmpty s (i+1) p in
TrieNode (opt, CharMap.add c sub map)
in
let trie =
List.fold_left
(fun trie (s, p) ->
if s = "" then invalid_arg "switch_s: empty string";
add_trie trie s 0 p
) TrieEmpty l
in
SwitchS trie
let bool =
switch_s
[ "true", Return true
; "false", Return false
]
let fix f = Fix f
module Infix = struct
let (>|=) x f = map f x
let (<*>) = app
let (<<) a b = AppLeft (a, b) (* return (fun x y -> x) <*> a <*> b *)
let (>>) a b = AppRight (a, b) (* return (fun x y -> y) <*> a <*> b *)
let (<+>) a b = choice [a; b]
end
include Infix
(* TODO: more efficient version, with buffer *)
let word =
return (fun c s -> string_of_list (c :: s)) <*> alpha <*> many alpha_num
(** {2 Signatures} *)
type error = {
line: int;
col: int;
msg: string;
}
let string_of_error e = str "at %d:%d; %s" e.line e.col e.msg
exception Error of error
module type S = sig
type source
(** Source of characters *)
val parse : source -> 'a t -> ('a, error) result
(** Parse the given source using the parser, and returns the parsed value. *)
val parse': source -> 'a t -> ('a, string) result
(** Same as {!parse}, but returns a user-friendly string in case of failure *)
val parse_exn : source -> 'a t -> 'a
(** Unsafe version of {!parse}.
@raise Error if parsing fails *)
end
(** {2 Build a parser from a given Monadic Input} *)
module type INPUT = sig
type t
val read : t -> Bytes.t -> int -> int -> int
end
type token =
| Yield of char
| EOF
module type READER = sig
type t
type source
val create : source -> t
val peek : t -> token (* peek; do not consume *)
val next : t -> token (* read and consume *)
val junk : t -> unit (* consume last token, obtained with junk *)
val line : t -> int
val col : t -> int
end
module ReaderOfInput(I : INPUT) : READER with type source = I.t = struct
type t = {
mutable rline : int;
mutable rcol : int;
input : I.t;
buf : Bytes.t;
mutable i : int;
mutable len : int;
}
type source = I.t
let line t = t.rline
let col t = t.rcol
let create input = {
rline=0;
rcol=0;
input;
buf = Bytes.make 1024 ' ';
i=1;
len=1; (* trick for initialization *)
}
let read_next t =
let c = Bytes.get t.buf t.i in
t.i <- t.i + 1;
if c = '\n' then (
t.rcol <- 0;
t.rline <- t.rline + 1;
) else (
t.rcol <- t.rcol + 1
);
Yield c
let refill t =
t.len <- I.read t.input t.buf 0 (Bytes.length t.buf);
t.i <- 0;
()
let next t =
if t.len = 0 then EOF
else if t.i = t.len
then (
refill t;
if t.len = 0 then EOF else read_next t
) else read_next t
let peek t =
if t.i = t.len
then refill t;
Yield (Bytes.get t.buf t.i)
let junk t =
assert (t.len > 0 && t.i < t.len);
t.i <- t.i + 1
end
module MakeFromReader(R : READER) : S with type source = R.source = struct
type source = R.source
let error r msg =
raise (Error {
line = R.line r;
col = R.col r;
msg;
})
let errorf r fmt =
Printf.ksprintf
(fun msg -> error r msg)
fmt
let is_int c = Char.code c >= Char.code '0' && Char.code c <= Char.code '9'
let to_int c = Char.code c - Char.code '0'
let rec parse_int r sign i = match R.peek r with
| EOF -> i
| Yield c when is_int c ->
R.junk r;
parse_int r sign (10 * i + to_int c)
| Yield '-' when i = 0 && sign ->
(* switch sign: only on first char *)
R.junk r;
parse_int r false 0
| _ -> if sign then i else -i
let parse_float _r _buf = assert false
let rec parse_rec : type a. R.t -> a t -> a =
fun r p -> match p with
| Return x -> x
| Map (f, x) ->
let y = parse_rec r x in
f y
| Filter (f, x) ->
let y = parse_rec r x in
if f y then y else errorf r "filter failed"
| App (f, x) ->
let f' = parse_rec r f in
let x' = parse_rec r x in
f' x'
| AppLeft (a, b) ->
let a' = parse_rec r a in
let _ = parse_rec r b in
a'
| AppRight (a, b) ->
let _ = parse_rec r a in
let b' = parse_rec r b in
b'
| Fail msg -> error r msg
| Int -> parse_int r true 0
| Float -> parse_float r (Buffer.create 8)
| AnyOf set ->
begin match R.next r with
| EOF -> errorf r "expected any of {%s}, got EOF" (print_char_set set)
| Yield c ->
if CharSet.mem c set then c
else errorf r "expected any of {%s}, got %c" (print_char_set set) c
end
| Many (set, p, sep, mult) -> parse_many r ~set ~sep ~p ~mult []
| Skip (set, p, mult) -> parse_skip r ~set ~p ~mult
| SwitchC (map, def) ->
begin match R.peek r with
| EOF -> errorf r "expected any of {%s}, got EOF" (print_char_map map)
| Yield c ->
begin try
let p' = CharMap.find c map in
parse_rec r p'
with Not_found ->
match def with
| None ->
errorf r "expected any of {%s}, got %c" (print_char_map map) c
| Some d -> parse_rec r d
end
end
| SwitchS TrieEmpty -> assert false
| SwitchS (TrieNode (Some p, _)) ->
parse_rec r p
| SwitchS (TrieNode (None, map)) ->
begin match R.next r with
| EOF -> errorf r "expected any of {%s}, got EOF" (print_char_map map)
| Yield c ->
begin try
let trie = CharMap.find c map in
parse_rec r (SwitchS trie) (* recurse in subtree *)
with Not_found ->
errorf r "expected any of {%s}, got %c" (print_char_map map) c
end
end
| Fix f ->
let p = f (Fix f) in
parse_rec r p
| Eof ->
begin match R.next r with
| EOF -> ()
| Yield c -> errorf r "expected EOF, got %c" c
end
and parse_many
: type a. R.t -> set:CharSet.t -> p:a t -> sep:unit t ->
mult:multiplicity -> a list -> a list
= fun r ~set ~p ~sep ~mult acc ->
match R.peek r with
| EOF -> List.rev acc
| Yield c ->
if CharSet.mem c set
then
let x = parse_rec r p in
match mult with
| Question -> assert (acc = []); [x]
| Plus | Star ->
let _ = parse_rec r sep in (* separator *)
parse_many r ~set ~p ~sep ~mult:Star (x::acc)
else if mult = Plus
then errorf r "expected {%s}, got %c" (print_char_set set) c
else List.rev acc
and parse_skip
: type a. R.t -> set:CharSet.t -> p:a t -> mult:multiplicity -> unit
= fun r ~set ~p ~mult ->
match R.peek r with
| EOF -> ()
| Yield c ->
if CharSet.mem c set
then
let _ = parse_rec r p in
match mult with
| Question -> ()
| Plus | Star -> parse_skip r ~set ~p ~mult:Star
else if mult = Plus
then errorf r "expected {%s}, got %c" (print_char_set set) c
else ()
(* public functions *)
let parse_exn src p =
let r = R.create src in
parse_rec r p
let parse src p =
let r = R.create src in
try
`Ok (parse_rec r p)
with Error e ->
`Error e
let parse' src p = match parse src p with
| `Ok x -> `Ok x
| `Error e -> `Error (string_of_error e)
end
module Make(I : INPUT) = struct
module R = ReaderOfInput(I)
include MakeFromReader(R)
end
module Str = MakeFromReader(struct
(* reader of string *)
type t = {
str : string;
mutable i : int;
mutable rcol : int;
mutable rline : int;
}
type source = string
let create str = {
str;
i = 0;
rcol = 1;
rline = 1;
}
let line t = t.rline
let col t = t.rcol
let peek t =
if t.i = String.length t.str then EOF else Yield (String.get t.str t.i)
let junk t =
assert (t.i < String.length t.str);
t.i <- t.i + 1
let next t =
if t.i = String.length t.str then EOF
else (
let c = String.get t.str t.i in
t.i <- t.i + 1;
if c = '\n' then (
t.rcol <- 1;
t.rline <- t.rline + 1
) else t.rcol <- t.rcol + 1;
Yield c
)
end)
module Chan = Make(struct
type t = in_channel
let read = input
end)

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(*
copyright (c) 2013-2015, simon cruanes
all rights reserved.
redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer. redistributions in binary
form must reproduce the above copyright notice, this list of conditions and the
following disclaimer in the documentation and/or other materials provided with
the distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*)
(** {1 Applicative Parser Combinators}
{b status: experimental}
@since NEXT_RELEASE
*)
type ('a,'b) result = [`Error of 'b | `Ok of 'a]
type 'a t
(** Parser that yields an error or a value of type 'a *)
(** {6 Combinators} *)
val return : 'a -> 'a t
(** Parser that succeeds with the given value *)
val fail : string -> 'a t
(** [fail msg] fails with the given error message *)
(* TODO: a format version of fail *)
val app : ('a -> 'b) t -> 'a t -> 'b t
(** Applicative *)
val map : ('a -> 'b) -> 'a t -> 'b t
(** Map the parsed value *)
val int : int t
(** Parse an integer *)
val float : float t
(** Parse a floating point number *)
val bool : bool t
(** Parse "true" or "false" *)
val char : char -> char t
(** [char c] parses [c] and [c] only *)
val any_of : string -> char t
(** Parse any of the chars present in the given string *)
val alpha_lower : char t
val alpha_upper : char t
val alpha : char t
val num : char t
val alpha_num : char t
val word : string t
(** [word] parses any identifier not starting with an integer and
not containing any whitespace nor delimiter
TODO: specify *)
val spaces : unit t
(** Parse a sequence of ['\t'] and [' '] *)
val spaces1 : unit t
(** Same as {!spaces} but requires at least one space *)
val white : unit t
(** Parse a sequence of ['\t'], ['\n'] and [' '] *)
val white1 : unit t
val eof : unit t
(** Matches the end of input, fails otherwise *)
val many : ?sep:unit t -> 'a t -> 'a list t
(** 0 or more parsed elements of the given type.
@param sep separator between elements of the list (for instance, {!space}) *)
val many1 : ?sep:unit t -> 'a t -> 'a list t
(** Same as {!many}, but needs at least one element *)
val skip : _ t -> unit t
(** Skip 0 or more instances of the given parser *)
val skip1 : _ t -> unit t
val opt : 'a t -> 'a option t
(** [opt x] tries to parse [x], and returns [None] otherwise *)
val filter : ('a -> bool) -> 'a t -> 'a t
(** [filter f p] parses the same as [p], but fails if the returned value
does not satisfy [f] *)
val switch_c : ?default:'a t -> (char * 'a t) list -> 'a t
(** [switch_c l] matches the next char and uses the corresponding parser.
Fails if the next char is not in the list, unless default is defined.
@param default parser to use if no char matches
@raise Invalid_argument if some char occurs several times in [l] *)
val switch_s : (string * 'a t) list -> 'a t
(** [switch_s l] attempts to match matches any of the strings in [l].
If one of those strings matches, the corresponding parser
is used from now on.
@raise Invalid_argument if some string is a prefix of another string,
or is empty, or if the list is empty *)
val choice : 'a t list -> 'a t
(** [choice l] chooses between the parsers, unambiguously
@raise Invalid_argument if the list is empty, or if some parsers
overlap, making the choice ambiguous *)
val fix : ('a t -> 'a t) -> 'a t
(** [fix f] makes a fixpoint *)
module Infix : sig
val (>|=) : 'a t -> ('a -> 'b) -> 'b t
val (<*>) : ('a -> 'b) t -> 'a t -> 'b t
(** Synonym to {!app} *)
val (>>) : _ t -> 'a t -> 'a t
(** [a >> b] parses [a], ignores its result, then parses [b] *)
val (<<) : 'a t -> _ t -> 'a t
(** [a << b] parses [a], then [b], and discards [b] to return [a] *)
val (<+>) : 'a t -> 'a t -> 'a t
(** [a <+> b] is [choice [a;b]], a binary choice *)
end
include module type of Infix
(** {2 Signatures} *)
(** {6 Parsing} *)
type error = {
line: int;
col: int;
msg: string;
}
val string_of_error : error -> string
exception Error of error
module type S = sig
type source
(** Source of characters *)
val parse : source -> 'a t -> ('a, error) result
(** Parse the given source using the parser, and returns the parsed value. *)
val parse': source -> 'a t -> ('a, string) result
(** Same as {!parse}, but returns a user-friendly string in case of failure *)
val parse_exn : source -> 'a t -> 'a
(** Unsafe version of {!parse}.
@raise Error if parsing fails *)
end
(** {2 Parse} *)
module type INPUT = sig
type t
val read : t -> Bytes.t -> int -> int -> int
end
module Make(I : INPUT) : S with type source = I.t
(** {2 Low-level interface} *)
type token =
| Yield of char
| EOF
module type READER = sig
type t
type source (* underlying source *)
val create : source -> t
val peek : t -> token (* peek; do not consume *)
val next : t -> token (* read and consume *)
val junk : t -> unit (* consume last token, obtained with junk *)
val line : t -> int
val col : t -> int
end
module MakeFromReader(R : READER) : S with type source = R.source
(** {2 Defaults} *)
module Str : S with type source = string
module Chan : S with type source = in_channel