cairn 1.0 (latest) · OCaml Package

This module define a type configuration representing the configuration of a parser, and a type action representing the actions that can be applied to a parser configuration, only with types independent of any menhir type. These objects are intended as logs for a parser, and helper functions are provided to modify them and display them (including a TUI).

If you are only using this module alongside Parsing, then you should not really need this module, or at the limit, the functions print_configuration, print_configuration_list and derivations_explorer might be of use.

If you want to log a handmade parser, then you should start by creating an initial configuration with initialConfiguration, and then, construct a list of configuration by applying to the first element the action your parser is performing (with apply_action). For the sake of simpler log, the Shift action has been merged with the next Input action. pop_configuration allow you to pop the stack (for error treatment). The rest of the functions should help you if you want another UI or log of the configurations.

author Vincent Penelle <vincent.penelle@u-bordeaux.fr>.

type action =

| ShiftRead of int * string * string
(*
ShiftRead(state,token,str) : Shifts the lookahead to state number state as token token (string representation) and reads str as new lookahead.
*)
| Input of string
(*
Input(str) : Reads str as the new lookahead.
*)
| Reduce of string * string * int * int
(*
Reduce(nonTerm,production,state,size) : Reduces the production production (string representation) to state number state. The lefthand of the production is nonTerm and the size of the righthand of the production is size. Those informations are used to display information correctly.
*)
| Accept
(*
The parser is accepting.
*)
| Reject
(*
The parser is rejecting.
*)
| Error of string * string * string
(*
Error(location,indication,message) : The parser is in an error state. location is a string describing the position of the error in the parsed text, indication is a string telling between which characters the error was encountered, and message is a string describing the nature of the error.
*)

Type representing the actions that can be applied to a LR1 parser.

val string_of_action : action -> string

Returns a string description of the provided action.

type configuration

Type representing the configuration of a LR1 parser, i.e., its state (number), the stack (and for each element of it, the partial derivation tree associated with it), the lookahead, and the last action applied to it. The parser itself is not known by such an element, and the representation is only composed of integer and string (no types depending of a parser).

val initial_configuration : configuration

An initial configuration : state number 0, the empty stack, no lookahead and action Reading.

val get_top_state : configuration -> int

Returns the number of the state that is the current parser configuration.

val pop_configuration : configuration -> configuration

Pops the last element of the stack if there is one (leaves the empty stack unchanged).

val apply_action : configuration -> action -> configuration

apply_action configuration action produces the effect of the action action to the configuration configuration. Does NOT check that the action makes sense (as it is only textual representation) and may raise an exception if trying to apply Reduce with a size bigger than the size of the stack of configuration.

val markup_of_configuration : 
  bool ->
  bool ->
  configuration ->
  string * string * LTerm_text.item list list

let str_act,str_look,repr_deriv = markup_of_configuration color utf8 configuration produces a LTerm representation of the given parser configuration.

str_act is the string representation of the last action applied
str_look is the lookahead of the parser
repr_deriv is a LTerm_text.item list representation of the partial derivation trees on the stack of configuration. Each element of the list is a line of the representation.

If color is true, then the root of the topmost tree (i.e., the last symbol added) will be in green, otherwise no color will be present
If utf8 is true, then the tree will use utf8 characters for better depiction, otherwise only ASCII symbol will be present

val stringlist_of_configuration : 
  bool ->
  configuration ->
  string * string * string list

let str_act,str_look,repr_deriv = stringlist_of_configuration utf8 configuration produces the same representation as markup_of_configuration except that the list is directly composed of strings. Useful if not destined to a LTerm application (e.g., for displaying in a log).

val stack_of_configuration : configuration -> string list

strack_of_configuration configuration returns the list of non-terminals (their string representation) composing the stack of configuration.

val print_configuration : Format.formatter -> configuration -> unit

Pretty printer for a configuration.

val print_configuration_list : Format.formatter -> configuration list -> unit

Pretty printer for a list of configuration sequence (representing the execution of a parser).

val derivations_explorer : configuration list -> (int -> string list) -> unit

derivations_explorer configurations state_repr executes a TUI allowing to explore the list of configurations configurations. state_repr associates to each state number a list of string representing its LR0 components.

package cairn