J syntax

J program

With J syntax, UML profiles, class attributes and methods have to be declared in the right order.

Program::=

{attribute_declaration}

{method_definition}

Class attributes

J class attributes can be declared with an initial value.

attribute_declaration::=

class ':' [profile] attribute_name ':'

class [assignment]';'

Method declaration

Method declaration is made up of the class which owns the method, its UML profile and its name, followed by its parameters and its possible return value.

method_definition::=

class ':' [profile] method_specification

method_specification::=

method_name parameter_designation_list

[return class]

parameter_designation_list::=

'(' [ <parameter_designation>

{',' <parameter_designation>}])'

parameter_designation::=

passing_mode class parameter_name

passing_mode::= 'in'|'inout'

Designating UML profiles

The designation of the UML profile is useful, either to declare a method, or to define explicitly the UML profile during the message sending. The designation of the UML profile is in absolute mode (starting from "default" or "#"), or relative mode (starting from the current UML profile and possibly using the moving up "-").

UML profile::=

[header_profile] [{profile_item}]
profile_name profile_mode

header_profile::= <default |'#'>;

profile item::= profile_name '#';

profile_name::= <name | '-'>;

profile_mode::= <'#' | '##' >;

Designating a class

Classes are predefined, and will be either basic classes (integer, …), or metamodel classes. The "[]" prefix is used to designate sets.

Class::= class | class'[]'

Defining blocks of instructions

Blocks of instructions appear either to define the content of the methods, or to define anonymous methods, linked to the sets resulting from a "select" or "while" command. At the head of each block, local variables can be defined.

Block::=

'{'

{variable_declaration}

{statement}

'}'

Declaring local variables

Local variables are declared at the head of each block. They can have an initial value.

variable_declaration::=

class variable_name [assignment]

Instructions

Instructions can be:

· a condition (if, else, etc.)

· an assignment (=, ?=)

· the sending of a message (object, method (parameter))

· a message diffusion (object.<method (parameter))

· the calling of an anonymous method

Statement::=

if_statement

| anonymous_statement

| message_call ';'

| [assign_statement] ';'

The "if" Instruction

The "if" instruction owns the "else" or " else if" operators, which allow you to easily combine several possible cases ("case" not being present).

if_statement::=

'if' '('expression')'

statement | compound_if_statement

['else' statement|compound_if_statement

compound_if_statement::=

'{'

{statement}

'}'

Assignment

assign_statement::= assignable assignment-operator expression

assignable::= variable_name|parameter_name|attribute_name

assignment operator::= '='|'?='

Message sending/Message diffusion

The sending of a message consists of accessing an object, then designating a method name and its parameters. Dynamic evaluation will launch the concerned method for the given object.

message_call::=

instance_access call_operator

[UML profile] method_name argument_list

instance_access::=[message_call | instance | iterator ]

{call_operator [message_call | instance |

iterator ]}

instance::= attribute_name | variable_name |

MetaModelInstance |

'this' | 'super' | 'StdOut' | 'StdErr'

iterator::= 'select' '(expression)' | 'while' '('expression')'

call_operator::= '.' | '.<'

argument_list::=

'('[<argument> {','argument}]')'

argument::= instance_access | integer_value | String_value

| boolean_value | method_statement | set_access | 'this'

Anonymous methods

An anonymous method always comes after an expression.

anonymous_statement::= message_call

Expressions

expression::= argument | boolean_expression | arithmetic_expression

| '('expression')'

boolean_expression::= expression '||' expression

| expression '&&' expression

| expression '==' expression

| expression '!=' expression

| expression relational_operator expression

| '!' expression

relational_operator::= '<' | '<=' | '>' | '>='

arithmetic_expression::= expression arith_op expression

arith_op::= '+' | '-' | '/' | '*' | '%'

J classes

J classes are basic classes, "stream" utility classes and metamodel classes.

basic_class::=

MetaModelClass | 'Object' | 'String' | 'boolean' | 'int'
| 'float' | 'inStream' | 'outStream' | 'stream'

Basic values

boolean value::= 'true' | 'false'

String_value::= Any symbol between " and "

int_value::= Any integer value