Logtalk reference manual

Grammar

The Logtalk grammar is here described using Backus-Naur Form syntax. Non-terminal symbols in italics have the definition found in the ISO Prolog Standard. Terminal symbols are represented in a fixed width font and between "".

Compilation units

entity ::=: object |; category |; protocol

Object definition

object ::=: begin_object_directive [object_directives] [clauses] end_object_directive.

begin_object_directive ::=: ":- object(" object_identifier [ "," object_relations] ")."

end_object_directive ::=: ":- end_object."

object_relations ::=: prototype_relations |; non_prototype_relations

prototype_relations ::=: prototype_relation |; prototype_relation "," prototype_relations

prototype_relation ::=: implements_protocols |; imports_categories |; extends_objects

non_prototype_relations ::=: non_prototype_relation |; non_prototype_relation "," non_prototype_relations

non_prototype_relation ::=: implements_protocols |; imports_categories |; instantiates_classes |; specializes_classes

Category definition

category ::=: begin_category_directive [category_directives] [clauses] end_category_directive.

begin_category_directive ::=: ":- category(" category_identifier [ "," category_relations] ")."

end_category_directive ::=: ":- end_category."

category_relations ::=: category_relation |; category_relation "," category_relations

category_relation ::=: implements_protocols |; imports_categories

Protocol definition

protocol ::=: begin_protocol_directive [protocol_directives] end_protocol_directive.

begin_protocol_directive ::=: ":- protocol(" protocol_identifier [ "," extends_protocols] ")."

end_protocol_directive ::=: ":- end_protocol."

Entity relations

implements_protocols ::=: "implements(" implemented_protocols ")"

extends_protocols ::=: "extends(" extended_protocols ")"

imports_categories ::=: "imports(" imported_categories ")"

extends_objects ::=: "extends(" extended_objects ")"

instantiates_classes ::=: "instantiates(" instantiated_objects ")"

specializes_classes ::=: "specializes(" specialized_objects ")"

Implemented protocols

implemented_protocols ::=: implemented_protocol |; implemented_protocol_sequence |; implemented_protocol_list

implemented_protocol ::=: protocol_identifier |; scope "::" protocol_identifier

implemented_protocol_sequence ::=: implemented_protocol |; implemented_protocol "," implemented_protocol_sequence

implemented_protocol_list ::=: "[" implemented_protocol_sequence "]"

Extended protocols

extended_protocols ::=: extended_protocol |; extended_protocol_sequence |; extended_protocol_list

extended_protocol ::=: protocol_identifier |; scope "::" protocol_identifier

extended_protocol_sequence ::=: extended_protocol |; extended_protocol "," extended_protocol_sequence

extended_protocol_list ::=: "[" extended_protocol_sequence "]"

Imported categories

imported_categories ::=: imported_category |; imported_category_sequence |; imported_category_list

imported_category ::=: category_identifier |; scope "::" category_identifier

imported_category_sequence ::=: imported_category |; imported_category "," imported_category_sequence

imported_category_list ::=: "[" imported_category_sequence "]"

Extended objects

extended_objects ::=: extended_object |; extended_object_sequence |; extended_object_list

extended_object ::=: object_identifier |; scope "::" object_identifier

extended_object_sequence ::=: extended_object |; extended_object "," extended_object_sequence

extended_object_list ::=: "[" extended_object_sequence "]"

Instantiated objects

instantiated_objects ::=: instantiated_object |; instantiated_object_sequence |; instantiated_object_list

instantiated_object ::=: object_identifier |; scope "::" object_identifier

instantiated_object_sequence ::=: instantiated_object; instantiated_object "," instantiated_object_sequence |

instantiated_object_list ::=: "[" instantiated_object_sequence "]"

Specialized objects

specialized_objects ::=: specialized_object |; specialized_object_sequence |; specialized_object_list

specialized_object ::=: object_identifier |; scope "::" object_identifier

specialized_object_sequence ::=: specialized_object |; specialized_object "," specialized_object_sequence

specialized_object_list ::=: "[" specialized_object_sequence "]"

Entity scope

scope ::=: "public" |; "protected" |; "private"

Entity identifiers

entity_identifiers ::=: entity_identifier |; entity_identifier_sequence |; entity_identifier_list

entity_identifier ::=: object_identifier |; protocol_identifier |; category_identifier

entity_identifier_sequence ::=: entity_identifier |; entity_identifier "," entity_identifier_sequence

entity_identifier_list ::=: "[" entity_identifier_sequence "]"

Object identifiers

object_identifiers ::=: object_identifier |; object_identifier_sequence |; object_identifier_list

object_identifier ::=: atom |; compound

object_identifier_sequence ::=: object_identifier |; object_identifier "," object_identifier_sequence

object_identifier_list ::=: "[" object_identifier_sequence "]"

Category identifiers

category_identifiers ::=: category_identifier |; category_identifier_sequence |; category_identifier_list

category_identifier ::=: atom

category_identifier_sequence ::=: category_identifier |; category_identifier "," category_identifier_sequence

category_identifier_list ::=: "[" category_identifier_sequence "]"

Protocol identifiers

protocol_identifiers ::=: protocol_identifier |; protocol_identifier_sequence |; protocol_identifier_list

protocol_identifier ::=: atom

protocol_identifier_sequence ::=: protocol_identifier |; protocol_identifier "," protocol_identifier_sequence

protocol_identifier_list ::=: "[" protocol_identifier_sequence "]"

Source file names

source_file_names ::=: source_file_name |; source_file_name_list

source_file_name ::=: atom |; library_source_file_name

library_source_file_name ::=: library_name "(" atom ")"

library_name ::=: atom

source_file_name_sequence ::=: source_file_name |; source_file_name "," source_file_name_sequence

source_file_name_list ::=: "[" source_file_name_sequence "]"

Directives

Source file directives

source_file_directives ::=: source_file_directive |; source_file_directive source_file_directives

source_file_directive ::=: ":- encoding(" atom ")." |; initialization_directive |; operator_directive

Object directives

object_directives ::=: object_directive |; object_directive object_directives

object_directive ::=: initialization_directive |; ":- threaded." |; ":- synchronized." |; ":- dynamic." |; ":- uses(" object_identifier ")." |; ":- calls(" protocol_identifiers ")." |; ":- info(" info_list ")." |; predicate_directives

Category directives

category_directives ::=: category_directive |; category_directive category_directives

category_directive ::=: initialization_directive |; ":- synchronized." |; ":- dynamic." |; ":- uses(" object_identifier ")." |; ":- calls(" protocol_identifiers ")." |; ":- info(" info_list ")." |; predicate_directives

Protocol directives

protocol_directives ::=: protocol_directive |; protocol_directive protocol_directives

protocol_directive ::=: initialization_directive |; ":- dynamic." |; ":- info(" info_list ")." |; predicate_directives

Predicate directives

predicate_directives ::=: predicate_directive |; predicate_directive predicate_directives

predicate_directive ::=: alias_directive |; synchronized_directive |; uses_directive |; scope_directive |; mode_directive |; meta_predicate_directive |; info_directive |; dynamic_directive |; discontiguous_directive |; operator_directive

alias_directive ::=: ":- alias(" entity_identifier "," predicate_indicator "," predicate_indicator ")." |; ":- alias(" entity_identifier "," non_terminal_indicator "," non_terminal_indicator ")."

synchronized_directive ::=: ":- synchronized(" predicate_indicator ")." |; ":- synchronized(" non_terminal_indicator ")."

uses_directive ::=: ":- uses(" object_identifier "," predicate_indicator_alias_list ")."

scope_directive ::=: ":- public(" predicate_indicator_term | non_terminal_indicator_term ")." |; ":- protected(" predicate_indicator_term | non_terminal_indicator_term ")." |; ":- private(" predicate_indicator_term | non_terminal_indicator_term ")."

mode_directive ::=: ":- mode(" predicate_mode_term | non_terminal_mode_term "," number_of_solutions ")."

meta_predicate_directive ::=: ":- meta_predicate(" meta_predicate_mode_indicator ")."

info_directive ::=: ":- info(" predicate_indicator | non_terminal_indicator "," info_list ")."

dynamic_directive ::=: ":- dynamic(" predicate_indicator_term | non_terminal_indicator_term ")." |

discontiguous_directive ::=: ":- discontiguous(" predicate_indicator_term | non_terminal_indicator_term ")." |

predicate_indicator_term ::=: predicate_indicator |; predicate_indicator_sequence |; predicate_indicator_list

predicate_indicator_sequence ::=: predicate_indicator |; predicate_indicator "," predicate_indicator_sequence

predicate_indicator_list ::=: "[" predicate_indicator_sequence "]"

predicate_indicator_alias ::=: predicate_indicator |; predicate_indicator "::" predicate_indicator

predicate_indicator_alias_sequence ::=: predicate_indicator_alias |; predicate_indicator_alias "," predicate_indicator_alias_sequence

predicate_indicator_alias_list ::=: "[" predicate_indicator_alias_sequence "]"

non_terminal_indicator_term ::=: non_terminal_indicator |; non_terminal_indicator_sequence |; non_terminal_indicator_list

non_terminal_indicator_sequence ::=: non_terminal_indicator |; non_terminal_indicator "," non_terminal_indicator_sequence

non_terminal_indicator_list ::=: "[" non_terminal_indicator_sequence "]"

non_terminal_indicator ::=: functor "//" arity

predicate_mode_term ::=: atom "(" mode_terms ")"

non_terminal_mode_term ::=: atom "(" mode_terms ")"

mode_terms ::=: mode_term |; mode_term "," mode_terms

mode_term ::=: "@" [type] | "+" [type] | "-" [type] | "?" [type]

type ::=: prolog_type | logtalk_type | user_defined_type

prolog_type ::=: "term" | "nonvar" | "var" |; "compound" | "ground" | "callable" | "list" |; "atomic" | "atom" |; "number" | "integer" | "float"

logtalk_type ::=: "object" | "category" | "protocol" |; "event"

user_defined_type ::=: atom |; compound

number_of_solutions ::=: "zero" | "zero_or_one" | "zero_or_more" | "one" | "one_or_more" | "error"

meta_predicate_mode_indicator ::=: atom "(" meta_predicate_terms ")"

meta_predicate_terms ::=: meta_predicate_term |; meta_predicate_term "," meta_predicate_terms

meta_predicate_term ::=: "::" | "*" | integer

info_list ::=: "[]" |; "[" info_item "is" nonvar "|" info_list "]"

info_item ::=: "comment" | "remarks" |; "author" | "version" | "date" |; "copyright" | "license" |; "parameters" | "parnames" |; "arguments" | "argnames" |; "definition" | "redefinition" | "allocation" |; "examples" | "exceptions" |; atom

Clauses and goals

goal ::=: message_call |; external_call |; callable

message_call ::=: message_to_object |; message_to_self |; message_to_super

message_to_object ::=: receivers "::" messages

message_to_self ::=: "::" messages

message_to_super ::=: "^^" message

messages ::=: message |; "(" message "," messages ")" |; "(" message ";" messages ")"

message ::=: callable |; variable

receivers ::=: receiver |; "(" receiver "," receivers ")" |; "(" receiver ";" receivers ")"

receiver ::=: object_identifier |; variable

external_call ::=: "{" callable "}"

Entity properties

category_property ::=: "static" |; "dynamic" |; "built_in" |; "synchronized"

object_property ::=: "static" |; "dynamic" |; "built_in" |; "synchronized" |; "threaded"

protocol_property ::=: "static" |; "dynamic" |; "built_in"

Predicate properties

predicate_property ::=: "static" |; "dynamic" |; "private" |; "protected" |; "public" |; "synchronized" |; "built_in" |; "declared_in(" entity_identifier ")" |; "defined_in(" object_identifier | category_identifier ")" |; "meta_predicate(" meta_predicate_mode_indicator ")" |; "alias(" callable ")" |; "non_terminal(" non_terminal_indicator ")"