package containers

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package containers
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Applicative Parser Combinators

Example: basic S-expr parser

open Containers_string.App_parse;;

type sexp = Atom of string | List of sexp list;;

let mkatom a = Atom a;;
let mklist l = List l;;

let ident_char = alpha_num <+> any_of "|!;$#@%&-_/=*.:~+[]<>'" ;;
let ident = many1 ident_char >|= str_of_l ;;
let atom = (ident <+> quoted) >|= mkatom ;;

let sexp = fix (fun sexp ->
  white >>
    (atom <+>
     ((char '(' >> many sexp << char ')') >|= mklist)
    )
);;

Str.parse_exn "(a (b c d) e)" sexp;;

status: experimental

  • since 0.10
type ('a, 'b) result = [
  1. | `Error of 'b
  2. | `Ok of 'a
]
type 'a t

Parser that yields an error or a value of type 'a

Combinators
val return : 'a -> 'a t

Parser that succeeds with the given value

val pure : 'a -> 'a t

Synonym to return

val junk : unit t

Skip next char

val fail : string -> 'a t

fail msg fails with the given error message

val failf : ('a, unit, string, 'b t) format4 -> 'a
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 symbols : char t

Symbols, such as "!-=_"...

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 quoted : string t

Quoted string, following OCaml conventions

val str_of_l : char list -> string

Helper to build strings from lists of chars

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.

  • parameter 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.

  • parameter default

    parser to use if no char matches

  • raises 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.

  • raises 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

  • raises 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 ... end
include module type of Infix
val (>|=) : 'a t -> ('a -> 'b) -> 'b t

Infix version of map

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

val (<::>) : 'a t -> 'a list t -> 'a list t

a <::> b is app (fun x l -> x::l) a b

Signatures

Parsing
type error = {
  1. line : int;
  2. col : int;
  3. msg : string;
}
val string_of_error : error -> string
exception Error of error
module type S = sig ... end

Parse

module type INPUT = sig ... end
module Make (I : INPUT) : S with type source = I.t

Low-level interface

val print : Format.formatter -> _ t -> unit

Print a parser structure, for debug purpose

type token =
  1. | Yield of char
  2. | EOF
module type READER = sig ... end
module MakeFromReader (R : READER) : S with type source = R.source

Defaults

module Str : S with type source = string
module Chan : S with type source = in_channel
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