Module `Parser_utils.Parser`

The Parser module collects an API of parser-combinators for parsing FIX messages into OCaml types. Each combinator takes a continuation function that returns a ( 'a Parser.t * msg ) type

type msg = (Imandra_prelude.string * Imandra_prelude.string) list: Type alias for a FIX message -- we assyme it is a list of string parirs

type 'a t = | ParseSuccess of 'a | UnknownMessageTag of Imandra_prelude.string | RequiredTagMissing of Imandra_prelude.string | DuplicateTag of Imandra_prelude.string | WrongValueFormat of Imandra_prelude.string | UndefinedTag of Imandra_prelude.string | EmptyValue of Imandra_prelude.string | IncorrectNumInGroupCount of Imandra_prelude.string | RepeatingGroupOutOfOrder of Imandra_prelude.string | GarbledMessage

val (>>=) : 'a t -> ('a -> 'b t) -> 'b t: A standard monadic bind operator for the Parser.t type

val (>|>=) : 'a t -> ('a -> 'b t * 'c list) -> 'b t * 'c list: The modified bind operator that applies a function that returns ( 'a Parser.t * msg ) pair

val rev_collect : 'a t list -> 'a list t: A "collect" function that convers 'a t list -> 'a list t Note: Tail-recursive, but reverses the list.

Each combinator takes the current message as the first argument and the continuation function as the last argument.

A typical message parser would look like this.

let parse_message msg = (
  repeating msg "1" parse_rg @@ fun msg group ->
  check_duplicate_tags msg   @@ fun () ->
  block     msg parse_blk    @@ fun msg block ->
  req msg "2" parse_int      @@ fun msg x -> 
  opt msg "3" parse_string   @@ fun msg y -> 
  req msg "4" parse_int      @@ fun msg z -> 
  ParseSuccess \{ block; group; x; y; z \}, msg 
) |> check_unknown_tags

val opt : (Imandra_prelude.string * Imandra_prelude.string) list -> Imandra_prelude.string -> (Imandra_prelude.string -> 'a option) -> ((Imandra_prelude.string * Imandra_prelude.string) list -> 'a option -> 'b t * 'c list) -> 'b t * 'c list: Optional field combinator, passes None into continuation if the tag is not present

val req : (Imandra_prelude.string * Imandra_prelude.string) list -> Imandra_prelude.string -> (Imandra_prelude.string -> 'a option) -> ((Imandra_prelude.string * Imandra_prelude.string) list -> 'a -> 'b t * 'c list) -> 'b t * 'c list: Required field combinator, returns RequiredTagMissing if the tag is not present

val block : msg -> (msg -> 'a t * msg) -> (msg -> 'a -> 'b t * msg) -> 'b t * msg: Block parser combinator parsers a record and passes it into the continuation

val repeating : msg -> Imandra_prelude.string -> (msg -> 'a t * msg) -> (msg -> 'a list -> 'b t * msg) -> 'b t * msg: Repeating group parser combinator, starting from the tag that encodes the length of the list, identifies the subgroups and passes each of them into the block parser. Performs a number of consistency checks on the parsed results.

val check_duplicate_tags : msg -> (Imandra_prelude.unit -> 'a t * msg) -> 'a t * msg: Checks for duplicate tags in messages -- should be called after all the repeating groups are porcessed

val check_unknown_tags : ('a t * (Imandra_prelude.string * 'b) list) -> 'a t: This finalizes the message -- if there are any unplrocessed tag=value pairs left -- we return an error

val get_top_and_last : 'a list -> 'a list * 'a option
val list_to_split : Imandra_prelude.string list -> char -> Imandra_prelude.string
val split_to_list : Imandra_prelude.string -> char -> Imandra_prelude.string list