package obus
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Monadic xml parsing

This module implements a simple monadic xml parser.

It is intended to make it easy to write XML document parsers. In OBus it is used to parse introspection document.

exception Parse_failure of Xmlm.pos * string
type xml_parser

Type of an xml parser. It is used to parse a sequence of arguments and children of an element.

type 'a node

Type of a single xml node parser, returning a value of type 'a

val failwith : xml_parser -> string -> 'a

Fail at current position with the given error message

val input : Xmlm.input -> 'a node -> 'a

Run a parser on a xml input. If it fails it raises a Parse_failure

Parsing of attributes

For the following functions, the first argument is the attribute name and each letter mean:

  • o : the attribute is optionnal
  • r : the attribute is required
  • d : a default value is given
  • f : a associative list for the attribute value is specified.
val ar : xml_parser -> string -> string
val ao : xml_parser -> string -> string option
val ad : xml_parser -> string -> string -> string
val afr : xml_parser -> string -> (string * 'a) list -> 'a
val afo : xml_parser -> string -> (string * 'a) list -> 'a option
val afd : xml_parser -> string -> 'a -> (string * 'a) list -> 'a
Parsing of elements
val elt : string -> (xml_parser -> 'a) -> 'a node

elt typ parser creates a node parser. It will parse element of type typ. parser is used to parse the attributes and children of the element.

Note that parser must consume all children, if some are left unparsed the parsing will fail.

val pcdata : string node

pcdata f parse one PCData

val map : 'a node -> ('a -> 'b) -> 'b node

map node f wraps the result of a node parser with f

val union : 'a node list -> 'a node

union nodes Node parser which parses any node matched by one of the given node parsers

Modifiers
val one : xml_parser -> 'a node -> 'a

one node parse exactly one node with the given node parser. It will fail if there is 0 or more than one node matched by node.

val opt : xml_parser -> 'a node -> 'a option

same as one but do not fail if there is no node matched by node.

val any : xml_parser -> 'a node -> 'a list

any node Parse all element matched by node. The resulting list is in the same order as the order in which nodes appears in the xml.