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basic json parser/printer using Genlex
This commit is contained in:
Simon Cruanes
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171
json.ml
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171
json.ml
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(*
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Copyright (c) 2013, Simon Cruanes
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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Redistributions of source code must retain the above copyright notice, this
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list of conditions and the following disclaimer. Redistributions in binary
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form must reproduce the above copyright notice, this list of conditions and the
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following disclaimer in the documentation and/or other materials provided with
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the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*)
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(** {1 Very simple JSON parser/printer} *)
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type t =
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| Int of int
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| Float of float
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| String of string
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| Null
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| Bool of bool
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| List of t list
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| Object of (string * t) list
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(** {2 Print/parse} *)
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let lex =
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Genlex.make_lexer ["{"; "}"; ":"; ","; "["; "]"; "true"; "false"; "null"]
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exception EOF
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let parse chars =
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let tokens = lex chars in
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let open Stream in
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let rec next () =
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match peek tokens with
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| None -> raise EOF (* end stream *)
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| Some (Genlex.Kwd "{") ->
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junk tokens;
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let args = read_pairs [] in
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(match peek tokens with
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| Some (Genlex.Kwd "}") ->
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junk tokens; Object args
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| _ -> raise (Stream.Error "expected '}'"))
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| Some (Genlex.Kwd "[") ->
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junk tokens;
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let args = read_list [] in
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(match peek tokens with
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| Some (Genlex.Kwd "]") ->
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junk tokens; List args
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| _ -> raise (Stream.Error "expected ']'"))
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| Some (Genlex.Int i) -> junk tokens; Int i
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| Some (Genlex.Float f) -> junk tokens; Float f
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| Some (Genlex.Kwd "true") -> junk tokens; Bool true
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| Some (Genlex.Kwd "false") -> junk tokens; Bool false
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| Some (Genlex.Kwd "null") -> junk tokens; Null
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| _ -> raise (Stream.Error "expected JSON value")
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and read_list acc =
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match peek tokens with
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| Some (Genlex.Kwd "]") -> List.rev acc (* yield *)
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| _ ->
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let t = next () in
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(match peek tokens with
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| Some (Genlex.Kwd ",") ->
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junk tokens;
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read_list (t::acc) (* next *)
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| Some (Genlex.Kwd "]") ->
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read_list (t::acc) (* next *)
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| Some (Genlex.Kwd "]") -> List.rev acc (* yield *)
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| _ -> raise (Stream.Error "expected ','"))
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and read_pairs acc =
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match peek tokens with
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| Some (Genlex.Kwd "}") -> List.rev acc (* yield *)
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| _ ->
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let k, v = pair () in
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(match peek tokens with
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| Some (Genlex.Kwd ",") ->
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junk tokens;
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read_pairs ((k,v)::acc) (* next *)
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| Some (Genlex.Kwd "}") ->
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read_pairs ((k,v)::acc) (* next *)
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| _ -> raise (Stream.Error "expected ','"))
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and pair () =
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match Stream.npeek 2 tokens with
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| [Genlex.String k; Genlex.Kwd ":"] ->
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junk tokens; junk tokens;
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let v = next () in
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k, v
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| _ -> raise (Stream.Error "expected pair")
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in
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Stream.from
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(fun _ ->
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try Some (next ())
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with EOF -> None)
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let parse_one chars =
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Stream.peek (parse chars)
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let rec output oc t =
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match t with
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| Null -> output_string oc "null"
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| Bool true -> output_string oc "true"
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| Bool false -> output_string oc "false"
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| Int i -> Printf.fprintf oc "%d" i
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| Float f -> Printf.fprintf oc "%f" f
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| String s -> Printf.fprintf oc "\"%s\"" (String.escaped s)
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| List l ->
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output_string oc "[";
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List.iteri
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(fun i t ->
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(if i > 0 then output_string oc ", ");
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output oc t)
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l;
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output_string oc "]"
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| Object pairs ->
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output_string oc "{";
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List.iteri
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(fun i (k,v) ->
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(if i > 0 then output_string oc ", ");
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Printf.fprintf oc "\"%s\": " k;
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output oc v)
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pairs;
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output_string oc "}"
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let rec pp fmt t =
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match t with
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| Null -> Format.pp_print_string fmt "null"
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| Bool true -> Format.pp_print_string fmt "true"
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| Bool false -> Format.pp_print_string fmt "false"
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| Int i -> Format.fprintf fmt "%d" i
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| Float f -> Format.fprintf fmt "%f" f
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| String s -> Format.fprintf fmt "\"%s\"" (String.escaped s)
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| List l ->
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Format.pp_print_string fmt "[";
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List.iteri
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(fun i t ->
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(if i > 0 then Format.pp_print_string fmt ", ");
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pp fmt t)
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l;
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Format.pp_print_string fmt "]"
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| Object pairs ->
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Format.pp_print_string fmt "{";
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List.iteri
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(fun i (k,v) ->
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(if i > 0 then Format.pp_print_string fmt ", ");
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Format.fprintf fmt "\"%s\": " k;
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pp fmt v)
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pairs;
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Format.pp_print_string fmt "}"
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let to_string t =
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let buf = Buffer.create 16 in
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Format.bprintf buf "%a@?" pp t;
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Buffer.contents buf
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(** {2 Utils *)
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exception TypeError of string * t
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62
json.mli
Normal file
62
json.mli
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@ -0,0 +1,62 @@
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(*
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Copyright (c) 2013, Simon Cruanes
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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Redistributions of source code must retain the above copyright notice, this
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list of conditions and the following disclaimer. Redistributions in binary
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form must reproduce the above copyright notice, this list of conditions and the
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following disclaimer in the documentation and/or other materials provided with
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the distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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|
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*)
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(** {1 Very simple JSON parser/printer} *)
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type t =
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| Int of int
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| String of string
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| Null
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| Bool of bool
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| List of t list
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| Object of (string * t) list
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(** {2 Print/parse} *)
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val parse : char Stream.t -> t Stream.t
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val parse_one : char Stream.t -> t option
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val output : out_channel -> t -> unit
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val pp : Format.formatter -> t -> unit
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val to_string : t -> string
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(** {2 Utils *)
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exception TypeError of string * t
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(*
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val to_int : t -> int
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val to_float : t -> float
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val to_string : t -> string
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val to_bool : t -> bool
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val to_null : t -> unit
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val to_list : t -> t list
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val to_object : t -> (string * t) list
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*)
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