nacc 1.0 · OCaml Package

Error report

type 'a state

Type state

type error

Type error

val state : 'a option -> int -> int -> string -> 'a state

Create a new parser state

val result_of_state : 'a state -> ('a, error) Stdlib.result

Get the result

val state_value : 'a state -> 'a option

Get the parsed value

val state_offset : 'a state -> int

Get the current position of the parser inside the string

val state_line : 'a state -> int

Get the current line position of the parser inside the string

val state_rest : 'a state -> string

Get the remaining characters of the string beeing parsed

val report : error -> unit

Report an error

Defining parsers

type 'a parser

Type parser

val (~~) : (string -> 'a state) -> 'a parser

Parser constructor

val pure : 'a -> 'a parser

Pure parser consuming no character and returning a value of type 'a.

val many : 'a parser -> 'a list parser

Parse zero or more times a given pattern

val some : 'a parser -> 'a list parser

Parse one or more times a given pattern

val check : (char -> bool) -> char parser

Test a predicate on the first character of the input. Resolve to this character if the predicate is verified

Combinators and Infix operators

val (<*>) : ('a -> 'b) parser -> 'a parser -> 'b parser

Apply

val (<$>) : ('a -> 'b) -> 'a parser -> 'b parser

Map

val (*>) : 'a parser -> 'b parser -> 'b parser

Apply to the right

val (<*) : 'a parser -> 'b parser -> 'a parser

Apply to the left

val (<|>) : 'a parser -> 'a parser -> 'a parser

Alternative

Let notation

val let* : 'a parser -> ('a -> 'b parser) -> 'b parser

Binding operator using the let* operator. This syntax is similar to Haskel's "do notation" :

let tuple_parser =
  let* f1 = floatingpoint in
  let* _ = char ',' in
  let* f2 = floatingpoint in
  pure (f1, f2)

Even if this operator can be usefull in extreme cases, users are encouraged to use the (<*>) operator instead :

let tuple_parser =
  (fun x y -> (x, y)) <$> floatingpoint <*> char ',' *> floatingpoint

Powerfull Combinators

The following operators are usefull to parse patterns which are left recursive by nature. The typical exemple is arithmetic expressions.

val chainl : ('a -> 'a -> 'a) parser -> 'a parser -> 'a parser

Eliminate left recursion in "left associative" chains. chainl op term is a parser recognizing chains of terms term bound by the operator op. The operator is considered left associative.

val chainr : 'a parser -> ('a -> 'a -> 'a) parser -> 'a parser

Eliminate left recursion in "right associative" chains. chainr term op is a parser recognizing chains of terms term bound by the operator op. The operator is considered right associative.

Utils

val do_parse : 'a parser -> string -> ('a, error) Stdlib.result

Run a parser against a string

val (-->) : string -> 'a parser -> 'a state

Feed a parser with a string (from left to right) This is verry different from do_parse ! No verifications are made on the remaining chars.

val (<--) : 'a parser -> string -> 'a state

Feed a parser with a string (from right to left) p <-- input is input --> p. This function is just for convenience.

val do_parse_from_file : 'a parser -> string -> ('a, error) Stdlib.result

Run a parser against a file