Logtalk reference manual
Grammar
Contents > Reference Manual > Grammar

# 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 double-quotes.

## Entities

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 |
  extends_categories |
  complements_objects

## 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

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

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

extends_categories ::=
  "`extends(`" extended_categories "`)`"

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

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

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

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

complements_objects ::=
  "`complements(`" complemented_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 "`]`"

### Extended categories

extended_categories ::=
  extended_category |
  extended_category_sequence |
  extended_category_list

extended_category ::=
  category_identifier |
  scope "`::`" category_identifier

extended_category_sequence ::=
  extended_category |
  extended_category "`,`" extended_category_sequence

extended_category_list ::=
  "`[`" extended_category_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 "`]`"

### Complemented objects

complemented_objects ::=
  object_identifier |
  complemented_object_sequence |
  complemented_object_list

complemented_object_sequence ::=
  object_identifier |
  object_identifier "`,`" complemented_object_sequence

complemented_object_list ::=
  "`[`" complemented_object_sequence "`]`"

### Entity and predicate 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 |
  compound

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 "`]`"

### Module identifiers

module_identifier ::=
  atom

## 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 "`).`" |
  "`:- set_logtalk_flag(`" atom "`,`" nonvar "`).`" |
  Prolog directives

### Conditional compilation directives

conditional_compilation_directives ::=
  conditional_compilation_directive |
  conditional_compilation_directive conditional_compilation_directives

conditional_compilation_directive ::=
  "`:- if(`" callable "`).`" |
  "`:- elif(`" callable "`).`" |
  "`:- else.`" |
  "`:- endif.`"

### Object directives

object_directives ::=
  object_directive |
  object_directive object_directives

object_directive ::=
  initialization_directive |
  "`:- built_in.`" |
  "`:- threaded.`" |
  "`:- dynamic.`" |
  "`:- uses(`" object_identifier "`).`" |
  "`:- use_module(`" module_identifier "`,`" module_predicate_indicator_alias_list "`).`" |
  "`:- calls(`" protocol_identifiers "`).`" |
  "`:- info(`" entity_info_list "`).`" |
  "`:- set_logtalk_flag(`" atom "`,`" nonvar "`).`" |
  predicate_directives

### Category directives

category_directives ::=
  category_directive |
  category_directive category_directives

category_directive ::=
  initialization_directive |
  "`:- built_in.`" |
  "`:- dynamic.`" |
  "`:- uses(`" object_identifier "`).`" |
  "`:- use_module(`" module_identifier "`,`" predicate_indicator_alias_list "`).`" |
  "`:- calls(`" protocol_identifiers "`).`" |
  "`:- info(`" entity_info_list "`).`" |
  "`:- set_logtalk_flag(`" atom "`,`" nonvar "`).`" |
  predicate_directives

### Protocol directives

protocol_directives ::=
  protocol_directive |
  protocol_directive protocol_directives

protocol_directive ::=
  initialization_directive |
  "`:- built_in.`" |
  "`:- dynamic.`" |
  "`:- info(`" entity_info_list "`).`" |
  "`:- set_logtalk_flag(`" atom "`,`" nonvar "`).`" |
  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 |
  meta_non_terminal_directive |
  info_directive |
  dynamic_directive |
  discontiguous_directive |
  multifile_directive |
  coinductive_directive |
  operator_directive

alias_directive ::=
  "`:- alias(`" entity_identifier "`,`" predicate_indicator_alias_list "`).`" |
  "`:- alias(`" entity_identifier "`,`" non_terminal_indicator_alias_list "`).`"

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_proofs "`).`"

meta_predicate_directive ::=
  "`:- meta_predicate(`" meta_predicate_template_term "`).`"

meta_non_terminal_directive ::=
  "`:- meta_non_terminal(`" meta_non_terminal_template_term "`).`"

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

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

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

multifile_directive ::=
  "`:- multifile(`" predicate_indicator_term "`).`"

coinductive_directive ::=
  "`:- coinductive(`" predicate_indicator_term | coinductive_predicate_template_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 "`as`" predicate_indicator |
  predicate_indicator "`::`" 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 "`]`"

module_predicate_indicator_alias ::=
  predicate_indicator |
  predicate_indicator "`as`" predicate_indicator |
  predicate_indicator "`:`" predicate_indicator

module_predicate_indicator_alias_sequence ::=
  module_predicate_indicator_alias |
  module_predicate_indicator_alias "`,`" module_predicate_indicator_alias_sequence

module_predicate_indicator_alias_list ::=
  "`[`" module_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

non_terminal_indicator_alias ::=
  non_terminal_indicator |
  non_terminal_indicator "`as`" non_terminal_indicator
  non_terminal_indicator "`::`" non_terminal_indicator

non_terminal_indicator_alias_sequence ::=
  non_terminal_indicator_alias |
  non_terminal_indicator_alias "`,`" non_terminal_indicator_alias_sequence

non_terminal_indicator_alias_list ::=
  "`[`" non_terminal_indicator_alias_sequence "`]`"

coinductive_predicate_template_term ::=
  coinductive_predicate_template |
  coinductive_predicate_template_sequence |
  coinductive_predicate_template_list

coinductive_predicate_template_sequence ::=
  coinductive_predicate_template |
  coinductive_predicate_template "`,`" coinductive_predicate_template_sequence

coinductive_predicate_template_list ::=
  "`[`" coinductive_predicate_template_sequence "`]`"

coinductive_predicate_template ::=
  atom "`(`" coinductive_mode_terms "`)`"

coinductive_mode_terms ::=
  coinductive_mode_term |
  coinductive_mode_terms "`,`" coinductive_mode_terms

coinductive_mode_term ::=
  "`+`" | "`-`"

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_proofs ::=
  "`zero`" | "`zero_or_one`" | "`zero_or_more`" | "`one`" | "`one_or_more`" | "`error`"

meta_predicate_template_term ::=
  meta_predicate_template |
  meta_predicate_template_sequence |
  meta_predicate_template_list

meta_predicate_template_sequence ::=
  meta_predicate_template |
  meta_predicate_template "`,`" meta_predicate_template_sequence

meta_predicate_template_list ::=
  "`[`" meta_predicate_template_sequence "`]`"

meta_predicate_template ::=
  object_identifier "`::`" atom "`(`" meta_predicate_specifiers "`)`" |
  category_identifier "`::`" atom "`(`" meta_predicate_specifiers "`)`" |
  atom "`(`" meta_predicate_specifiers "`)`"

meta_predicate_specifiers ::=
  meta_predicate_specifier |
  meta_predicate_specifier "`,`" meta_predicate_specifiers

meta_predicate_specifier ::=
  non-negative integer | "`::`" | "`^`" |
  "`*`"

meta_non_terminal_template_term ::=
  meta_predicate_template_term

entity_info_list ::=
  "`[]`" |
  "`[`" entity_info_item "`is`" nonvar "`|`" entity_info_list "`]`"

entity_info_item ::=
  "`comment`" | "`remarks`" |
  "`author`" | "`version`" | "`date`" |
  "`copyright`" | "`license`" |
  "`parameters`" | "`parnames`" |
  atom

predicate_info_list ::=
  "`[]`" |
  "`[`" predicate_info_item "`is`" nonvar "`|`" predicate_info_list "`]`"

predicate_info_item ::=
  "`comment`" |
  "`arguments`" | "`argnames`" |
  "`redefinition`" | "`allocation`" |
  "`examples`" | "`exceptions`" |
  atom

## Clauses and goals

clause ::=
  object_identifier "`::`" head "`:-`" body |
  head :- body |
  fact

goal ::=
  message_sending |
  super_call |
  external_call |
  context_switching_call |
  callable

message_sending ::=
  message_to_object |
  message_delegation |
  message_to_self

message_to_object ::=
  receiver "`::`" messages

message_delegation ::=
  "`[`" message_to_object "`]`"

message_to_self ::=
  "`::`" messages

super_call ::=
  "`^^`" message

messages ::=
  message |
  "`(`" message "`,`" messages "`)`" |
  "`(`" message "`;`" messages "`)`" |
  "`(`" message "`->`" messages "`)`"

message ::=
  callable |
  variable

receiver ::=
  "`{`" callable "`}`" |
  object_identifier |
  variable

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

context_switching_call ::=
  object_identifier "`<<`" goal

## Lambda expressions

lambda_expression ::=
  lambda_free_variables "`/`" lambda_parameters "`>>`" callable |
  lambda_free_variables "`/`" callable |
  lambda_parameters "`>>`" callable

lambda_free_variables ::=
  "`{`" conjunction of variables "`}`" |
  "`{`" variable "`}`" |
  "`{}`"

lambda_parameters ::=
  list of terms |
  "`[]`"

## Entity properties

category_property ::=
  "`static`" |
  "`dynamic`" |
  "`built_in`" |
  "`file(`" atom "`)`" |
  "`file(`" atom "`,`" atom "`)`" |
  "`lines(`" integer "`,`" integer "`)`" |
  "`events`" |
  "`source_data`" |
  "`public(`" predicate_indicator_list "`)`" |
  "`protected(`" predicate_indicator_list "`)`" |
  "`private(`" predicate_indicator_list "`)`" |
  "`declares(`" predicate_indicator "`,`" predicate_declaration_property_list "`)`" |
  "`defines(`" predicate_indicator "`,`" predicate_definition_property_list "`)`" |
  "`includes(`" predicate_indicator "`,`" object_identifier | category_identifier "`,`" predicate_definition_property_list "`)`" |
  "`provides(`" predicate_indicator "`,`" object_identifier | category_identifier "`,`" predicate_definition_property_list "`)`" |
  "`alias(`" predicate_indicator "`,`" predicate_alias_property_list "`)`" |
  "`calls(`" predicate_called "`,`" predicate_call_property_list "`)`" |
  "`number_of_clauses(`" integer "`)`" |
  "`number_of_user_clauses(`" integer "`)`"

object_property ::=
  "`static`" |
  "`dynamic`" |
  "`built_in`" |
  "`threaded`" |
  "`file(`" atom "`)`" |
  "`file(`" atom "`,`" atom "`)`" |
  "`lines(`" integer "`,`" integer "`)`" |
  "`context_switching_calls`" |
  "`dynamic_declarations`" |
  "`events`" |
  "`source_data`" |
  "`complements(`" "`allow`" | "`restrict`" "`)`" |
  "`complements`" |
  "`public(`" predicate_indicator_list "`)`" |
  "`protected(`" predicate_indicator_list "`)`" |
  "`private(`" predicate_indicator_list "`)`" |
  "`declares(`" predicate_indicator "`,`" predicate_declaration_property_list "`)`" |
  "`defines(`" predicate_indicator "`,`" predicate_definition_property_list "`)`" |
  "`includes(`" predicate_indicator "`,`" object_identifier | category_identifier "`,`" predicate_definition_property_list "`)`" |
  "`provides(`" predicate_indicator "`,`" object_identifier | category_identifier "`,`" predicate_definition_property_list "`)`"
  "`alias(`" predicate_indicator "`,`" predicate_alias_property_list "`)`" |
  "`calls(`" predicate_called "`,`" predicate_call_property_list "`)`" |
  "`number_of_clauses(`" integer "`)`" |
  "`number_of_user_clauses(`" integer "`)`"

protocol_property ::=
  "`static`" |
  "`dynamic`" |
  "`built_in`" |
  "`source_data`" |
  "`file(`" atom "`)`" |
  "`file(`" atom "`,`" atom "`)`" |
  "`lines(`" integer "`,`" integer "`)`" |
  "`public(`" predicate_indicator_list "`)`" |
  "`protected(`" predicate_indicator_list "`)`" |
  "`private(`" predicate_indicator_list "`)`" |
  "`declares(`" predicate_indicator "`,`" predicate_declaration_property_list "`)`" |
  "`alias(`" predicate_indicator "`,`" predicate_alias_property_list "`)`"

predicate_declaration_property_list ::=
  "`[`" predicate_declaration_property_sequence "`]`"

predicate_declaration_property_sequence ::=
  predicate_declaration_property |
  predicate_declaration_property "`,`" predicate_declaration_property_sequence

predicate_declaration_property ::=
  "`static`" | "`dynamic`" |
  "`scope(`" scope "`)`" |
  "`private`" | "`protected`" | "`public`" |
  "`coinductive`" |
  "`multifile`" |
  "`synchronized`" |
  "`meta_predicate(`" meta_predicate_template "`)`" |
  "`coinductive(`" coinductive_predicate_template "`)`" |
  "`non_terminal(`" non_terminal_indicator "`)`" |
  "`line_count(`" integer "`)`" |
  "`mode(`" predicate_mode_term | non_terminal_mode_term "`,`" number_of_proofs "`)`" |
  "`info(`" list "`)`"

predicate_definition_property_list ::=
  "`[`" predicate_definition_property_sequence "`]`"

predicate_definition_property_sequence ::=
  predicate_definition_property |
  predicate_definition_property "`,`" predicate_definition_property_sequence

predicate_definition_property ::=
  "`auxiliary`" |
  "`non_terminal(`" non_terminal_indicator "`)`" |
  "`line_count(`" integer "`)`" |
  "`number_of_clauses(`" integer "`)`"

predicate_alias_property_list ::=
  "`[`" predicate_alias_property_sequence "`]`"

predicate_alias_property_sequence ::=
  predicate_alias_property |
  predicate_alias_property "`,`" predicate_alias_property_sequence

predicate_alias_property ::=
  "`for(`" predicate_indicator "`)`" |
  "`from(`" entity_identifier "`)`" |
  "`non_terminal(`" non_terminal_indicator "`)`" |
  "`line_count(`" integer "`)`"

predicate_called ::=
  predicate_indicator |
  "`^^`" predicate_indicator |
  "`::`" predicate_indicator |
  variable "`::`" predicate_indicator |
  object_identifier "`::`" predicate_indicator |
  variable "`:`" predicate_indicator |
  module_identifier "`:`" predicate_indicator

predicate_call_property_list ::=
  "`[`" predicate_call_property_sequence "`]`"

predicate_call_property_sequence ::=
  predicate_call_property |
  predicate_call_property "`,`" predicate_call_property_sequence

predicate_call_property ::=
  "`caller(`" predicate_indicator "`)`" |
  "`line_count(`" integer "`)`" |
  "`as(`" predicate_indicator "`)`"

## Predicate properties

predicate_property ::=
  "`static`" | "`dynamic`" |
  "`scope(`" scope "`)`" |
  "`private`" | "`protected`" | "`public`" |
  "`logtalk`" | "`prolog`" | "`foreign`" |
  "`coinductive(`" coinductive_predicate_template "`)`" |
  "`multifile`" |
  "`synchronized`" |
  "`built_in`" |
  "`declared_in(`" entity_identifier "`)`" |
  "`defined_in(`" object_identifier | category_identifier "`)`" |
  "`redefined_from(`" object_identifier | category_identifier "`)`" |
  "`meta_predicate(`" meta_predicate_template "`)`" |
  "`alias_of(`" callable "`)`" |
  "`alias_declared_in(`" entity_identifier "`)`" |
  "`non_terminal(`" non_terminal_indicator "`)`" |
  "`mode(`" predicate_mode_term | non_terminal_mode_term "`,`" number_of_proofs "`)`" |
  "`info(`" list "`)`" |
  "`number_of_clauses(`" integer "`)`"
  "`declared_in(`" entity_identifier "`,`" integer "`)`" |
  "`defined_in(`" object_identifier | category_identifier "`,`" integer"`)`" |
  "`redefined_from(`" object_identifier | category_identifier "`,`" integer"`)`" |
  "`alias_declared_in(`" entity_identifier "`,`" integer"`)`"

## Compiler flags

compiler_flag ::=
  flag(flag_value)