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 Core 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_terms ] 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_terms ] 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 “]

Terms

Object terms

object_terms ::=
object_term |
object_term object_terms
object_term ::=
object_directive |
clause |
grammar_rule

Category terms

category_terms ::=
category_term |
category_term category_terms
category_term ::=
category_directive |
clause |
grammar_rule

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).” |
:- include(” source_file_name “).
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(callable).” |
:- built_in.” |
:- threaded.” |
:- dynamic.” |
:- info(” entity_info_list “).” |
:- set_logtalk_flag(atom,nonvar).” |
:- include(” source_file_name “).” |
:- uses(” object_alias_list “).” |
predicate_directives

Category directives

category_directives ::=
category_directive |
category_directive category_directives
category_directive ::=
:- built_in.” |
:- dynamic.” |
:- info(” entity_info_list “).” |
:- set_logtalk_flag(atom,nonvar).” |
:- include(” source_file_name “).” |
:- uses(” object_alias_list “).” |
predicate_directives

Protocol directives

protocol_directives ::=
protocol_directive |
protocol_directive protocol_directives
protocol_directive ::=
:- built_in.” |
:- dynamic.” |
:- info(” entity_info_list “).” |
:- set_logtalk_flag(atom,nonvar).” |
:- include(” source_file_name “).” |
predicate_directives

Predicate directives

predicate_directives ::=
predicate_directive |
predicate_directive predicate_directives
predicate_directive ::=
alias_directive |
synchronized_directive |
uses_directive |
use_module_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 | non_terminal_indicator_alias_list
).
synchronized_directive ::=
:- synchronized(” predicate_indicator_term | non_terminal_indicator_term “).
uses_directive ::=
:- uses(
object_identifier | parameter_variable “,
predicate_indicator_alias_list | non_terminal_indicator_alias_list | operator_list
).
use_module_directive ::=
:- use_module(
module_identifier | parameter_variable “,
module_predicate_indicator_alias_list | module_non_terminal_indicator_alias_list | operator_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(” qualified_predicate_indicator_term | qualified_non_terminal_indicator_term “).
discontiguous_directive ::=
:- discontiguous(” predicate_indicator_term |
non_terminal_indicator_term “).
multifile_directive ::=
:- multifile(” qualified_predicate_indicator_term |
qualified_non_terminal_indicator_term “).
coinductive_directive ::=
:- coinductive(” predicate_indicator_term |
coinductive_predicate_template_term “).
parameter_variable ::=
_variable_
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 “]
qualified_predicate_indicator_term ::=
qualified_predicate_indicator |
qualified_predicate_indicator_sequence |
qualified_predicate_indicator_list
qualified_predicate_indicator_sequence ::=
qualified_predicate_indicator |
qualified_predicate_indicator “,” qualified_predicate_indicator_sequence
qualified_predicate_indicator_list ::=
[” qualified_predicate_indicator_sequence “]
qualified_predicate_indicator ::=
predicate_indicator |
object_identifier “::” predicate_indicator |
category_identifier “::” predicate_indicator |
module_identifier “:” predicate_indicator
predicate_indicator_alias ::=
predicate_indicator |
predicate_indicatoraspredicate_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_indicatoraspredicate_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 “]
module_non_terminal_indicator_alias ::=
non_terminal_indicator |
non_terminal_indicatorasnon_terminal_indicator
non_terminal_indicator:non_terminal_indicator
module_non_terminal_indicator_alias_sequence ::=
module_non_terminal_indicator_alias |
module_non_terminal_indicator_alias “,” module_non_terminal_indicator_alias_sequence
module_non_terminal_indicator_alias_list ::=
[” module_non_terminal_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
qualified_non_terminal_indicator_term ::=
qualified_non_terminal_indicator |
qualified_non_terminal_indicator_sequence |
qualified_non_terminal_indicator_list
qualified_non_terminal_indicator_sequence ::=
qualified_non_terminal_indicator |
qualified_non_terminal_indicator “, ” qualified_non_terminal_indicator_sequence
qualified_non_terminal_indicator_list ::=
[” qualified_non_terminal_indicator_sequence “]
qualified_non_terminal_indicator ::=
non_terminal_indicator |
object_identifier “::” non_terminal_indicator |
category_identifier “::” non_terminal_indicator |
module_identifier “:” non_terminal_indicator
non_terminal_indicator_alias ::=
non_terminal_indicator |
non_terminal_indicatorasnon_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 “]
operator_sequence ::=
operator specification |
operator specification,
operator_sequence
operator_list ::=
[” operator_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 ] | “--” [ 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” | “one_or_error” | “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 “isnonvar|” entity_info_list
]
entity_info_item ::=
comment” | “remarks” |
author” | “version” | “date” |
copyright” | “license” |
parameters” | “parnames” |
see_also” |
atom
predicate_info_list ::=
[]” |
[” predicate_info_item “isnonvar|” predicate_info_list “]
predicate_info_item ::=
comment” | “remarks” |
arguments” | “argnames” |
redefinition” | “allocation” |
examples” | “exceptions” |
atom
object_alias ::=
object_identifier “as” object_identifier
object_alias_sequence ::=
object_alias |
object_alias “,” object_alias_sequence
object_alias_list ::=
[” object_alias_sequence “]

Clauses and goals

clause ::=
object_identifier “::head:-body |
module_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 “,” predicate_call_update_property_list “)” |
updates(” predicate “,” predicate_call_update_property_list “)” |
number_of_clauses(integer)” |
number_of_rules(integer)” |
number_of_user_clauses(integer)” |
number_of_user_rules(integer)” |
debugging
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 “,” predicate_call_update_property_list “)” |
updates(” predicate “,” predicate_call_update_property_list “)” |
number_of_clauses(integer)” |
number_of_rules(integer)” |
number_of_user_clauses(integer)
number_of_user_rules(integer)” |
module |”
debugging
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 “)” |
debugging
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 “)” |
include(atom)” |
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 ::=
inline” | “auxiliary” |
non_terminal(” non_terminal_indicator “)” |
include(atom)” |
line_count(integer)” |
number_of_clauses(integer)” |
number_of_rules(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 “)” |
include(atom)” |
line_count(integer)
predicate ::=
predicate_indicator |
^^” predicate_indicator |
::” predicate_indicator |
variable::” predicate_indicator |
object_identifier “::” predicate_indicator |
variable:” predicate_indicator |
module_identifier “:” predicate_indicator
predicate_call_update_property_list ::=
[” predicate_call_update_property_sequence “]
predicate_call_update_property_sequence ::=
predicate_call_update_property |
predicate_call_update_property “,
predicate_call_update_property_sequence
predicate_call_update_property ::=
caller(” predicate_indicator “)” |
include(atom)” |
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” |
inline” |
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)” |
number_of_rules(integer)” |
declared_in(” entity_identifier “,” line_count “)” |
defined_in(” object_identifier | category_identifier “,” line_count “)” |
redefined_from(” object_identifier | category_identifier “,” line_count “)” |
alias_declared_in(” entity_identifier “,” line_count “)
line_count ::=
integer

Compiler flags

compiler_flag ::=
flag(flag_value)