Extended Backus–Naur Form (EBNF)

Extended Backus–Naur Form (EBNF) is a type of formal syntax used to specify the structure of a programming language or other formal language. It is an extension of Backus-Naur Form (BNF), which was originally developed by John Backus and Peter Naur to describe the syntax of the Algol programming language.

EBNF adds several additional metasymbols to the original BNF metasymbols, which allows for a more concise and readable specification of a language's syntax. It is commonly used in the specification of programming languages, and is also sometimes used to describe the syntax of other types of formal languages, such as database query languages or markup languages.

Basic support for EBNF has been introduced in PlantUML.

Minimal binary diagram

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@startebnf
binaryDigit = "0" | "1";
@endebnf

All EBNF Elements

EBNF elements handled by PlantUML are described below.

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@startebnf
title All EBNF elements managed by PlantUML

(* Nodes *)
litteral = "a";
special = ? a ?;
rule = a;

(* Edges *)
required = a;
optional = [a];

zero_or_more = {a};
one_or_more = a, {a};
one_or_more_ebnf = {a}-;

zero_or_more_with_separator = [a, {',', a}];
one_or_more_with_separator = a, {',', a};
zero_or_more_with_terminator = {a, ','};
one_or_more_with_terminator = a, ',', {a, ','};
one_or_more_with_terminator_ebnf = {a, ','}-;

alternative = a | b;
group = (a | b) , c;
without_group = a | b , c;
@endebnf

Special sequence management with special-sequence-symbol "?"

You can manage special sequence with special-sequence-symbol "?".

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@startebnf
(* Example from §8.1 ISO-EBNF *)

h-tab = ? IS0 6429 character Horizontal Tabulation ? ;

new-line = { ? IS0 6429 character Carriage Return ? },
? IS0 6429 character Line Feed ?,
{ ? IS0 6429 character Carriage Return ? };

(* Other possible examples: *)
h-tab = ?Unicode U+0009?;
empty-special = ??;
@endebnf

[Ref. QA-16781]

Full repetition management with repetition-symbol "*"

You can manage repetition with repetition-symbol "*".

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@startebnf
(* Simplified Fortran example *)
Fortran_77_continuation_line = 5 * " ",  '[...]', 66 * [character];

(* Minimal test *)
test = 4 * '2';

(* Example of §5.7 Syntactic-factor of ISO EBNF *)
aa = "A";
bb = 3 * aa, "B";
cc = 3 * [aa], "C";
dd = {aa}, "D";
ee = aa, {aa}, "E";
ff = 3 * aa, 3 * [aa], "F";
gg = 3 * {aa}, "D";
@endebnf

[Ref. QA-16750]

Drawing mode

You can choice the drawing mode, and having a compacted mode by using !pragma compact command.

Expanded mode (by default)

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@startebnf
title Expanded mode

zero_or_more = {a};
one_or_more = a, {a};
one_or_more_ebnf = {a}-;

zero_or_more_with_separator = [a, {',', a}];
one_or_more_with_separator = a, {',', a};
zero_or_more_with_terminator = {a, ','};
one_or_more_with_terminator = a, ',', {a, ','};

@endebnf

Compacted mode

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@startebnf
!pragma compact
title Compacted mode

zero_or_more = {a};
one_or_more = a, {a};
one_or_more_ebnf = {a}-;

zero_or_more_with_separator = [a, {',', a}];
one_or_more_with_separator = a, {',', a};
zero_or_more_with_terminator = {a, ','};
one_or_more_with_terminator = a, ',', {a, ','};

@endebnf

[Ref. QA-16692, QA-16529]

Notes on Elements

Notes may be added to elements of your diagram by using EBNF comment tags.

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@startebnf
title Comments
(* Notes for Rule1 *)
Rule1 = {"a-z" (* any letter *) };
(* Notes for Rule2 *)
Rule2 =;
(* Additional notes and references *)
@endebnf

Using (global) style

Without style (by default)

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@startebnf
title Title
not_styled_ebnf = {"a", c , "a" (* Note on a *)}
| ? special ?
| "repetition", 4 * '2';
(* Global End Note *)
@endebnf

With style

You can use style to change rendering of elements.

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@startebnf
<style>
element {
  ebnf {
    LineColor blue
    Fontcolor green
    Backgroundcolor palegreen
    note {
      Backgroundcolor pink
    }
  }
}
</style>
title Title
styled_ebnf = {"a", c , "a" (* Note on a *)}
| ? special ?
| "repetition", 4 * '2';
(* Global End Note *)
@endebnf

[Ref. QA-16529]

Example of LISP Grammar

LISP Grammar with PlantUML.

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@startebnf
title LISP Grammar
grammars_expression = atomic_symbol | "(", s_expression, ".", s_expression, ")" | list;
list = "(", s_expression, { s_expression }, ")";
atomic_symbol = letter, atom_part;
atom_part = empty | letter, atom_part | number, atom_part;
letter = ? a-z ?;
number = ? 1-9 ?;
empty = " ";
@endebnf

[Ref. ]

EBNF of PlantUMLs EBNF Grammar

EBNF allows for self description, so here it is!

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@startebnf
grammar = { rule };
rule = lhs , "=" (* definition *) , rhs , ";" (* termination *);
lhs = identifier ;
rhs = identifier
     | terminal
     | "[" , rhs (* optional *) , "]"
     | "{" , rhs (* repetition *), "}"
     | "(" , rhs (* grouping *) , ")"
     | "(*" , string (* comment *) , "*)"
     | "?" , rhs (* special sequence, aka notation *) , "?"
     | rhs , "|" (* alternation *) , rhs
     | rhs , "," (* concatenation *), rhs ;
identifier = letter , { letter | digit | "_" } ;
terminal = "'" , character , { character } , "'"
         | '"' , character , { character } , '"' ;
character = letter | digit | symbol | "_" ;
symbol = "[" | "]" | "{" | "}" | "(" | ")" | "<" | ">"
       | "'" | '"' | "=" | "|" | "." | "," | ";" ;
digit = ? 0-9 ? ;
letter = ? A-Z or a-z ? ;
@endebnf

Java Language Specification

A real world example of a detailed programming language.

Packages and Modules

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@startebnf
CompilationUnit = OrdinaryCompilationUnit | ModularCompilationUnit;
OrdinaryCompilationUnit = [PackageDeclaration], {ImportDeclaration}, {TopLevelClassOrInterfaceDeclaration};
ModularCompilationUnit = {ImportDeclaration}, ModuleDeclaration;
PackageDeclaration = {PackageModifier}, "package", Identifier, {Identifier}, ";";
PackageModifier = Annotation;
ImportDeclaration = SingleTypeImportDeclaration | TypeImportOnDemandDeclaration | SingleStaticImportDeclaration | StaticImportOnDemandDeclaration;
SingleTypeImportDeclaration = "import", TypeName, ";";
TypeImportOnDemandDeclaration = "import", PackageOrTypeName, ".*", ";";
SingleStaticImportDeclaration = "import", "static", TypeName, ".", Identifier, ";";
StaticImportOnDemandDeclaration = "import", "static", TypeName, ".*", ";";
TopLevelClassOrInterfaceDeclaration = (ClassDeclaration | InterfaceDeclaration), ";";
ModuleDeclaration = {Annotation}, [open], "module", Identifier, {Identifier}, "{", {ModuleDirective} "}";
ModuleDirective = ("requires", {RequiresModifier}, ModuleName, ";") | ("exports", PackageName, ["to", ModuleName {"," ModuleName}], ";") | ("opens", PackageName, ["to" ModuleName {"," ModuleName}], ";") | ("uses", TypeName, ";") | ("provides", TypeName, "with", TypeName {"," TypeName}, ";");
RequiresModifier = "transitive" | "static";
@endebnf

Lexical Structure

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@startebnf
Identifier = ?IdentifierChars but not a ReservedKeyword or BooleanLiteral or NullLiteral?;
IdentifierChars = JavaLetter, {JavaLetterOrDigit};
JavaLetter = ? any Unicode character that is a "Java letter" ?;
JavaLetterOrDigit = ? any Unicode character that is a "Java letter-or-digit" ?;
TypeIdentifier = ? Identifier but not permits, record, sealed, var, or yield ?;
UnqualifiedMethodIdentifier = ? Identifier but not yield ?;
Literal = IntegerLiteral | FloatingPointLiteral | BooleanLiteral | CharacterLiteral | StringLiteral | TextBlock | NullLiteral;
@endebnf

Types, Values, and Variables

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@startebnf
Type = PrimitiveType | ReferenceType;
PrimitiveType = [Annotation], (NumericType | boolean );
NumericType = IntegralType | FloatingPointType;
IntegralType = "byte" | "short" | "int" | "long" | "char";
FloatingPointType = "float" | "double";
ReferenceType = ClassOrInterfaceType | TypeVariable | ArrayType;
ClassOrInterfaceType = ClassType | InterfaceType;
ClassType = {Annotation}, TypeIdentifier, [TypeArguments];
PackageName = {Annotation}, TypeIdentifier, [TypeArguments];
ClassOrInterfaceType = {Annotation}, TypeIdentifier, [TypeArguments];
InterfaceType = ClassType;
TypeVariable = {Annotation}, TypeIdentifier;
ArrayType = (PrimitiveType | ClassOrInterfaceType | TypeVariable), Dims;
Dims=  {Annotation}, "[", "]", {{Annotation}, "[", "]"};
TypeParameter = {TypeParameterModifier}, TypeIdentifier, [TypeBound];
TypeParameterModifier = Annotation;
TypeBound = ("extends", TypeVariable) | ("extends" ClassOrInterfaceType {AdditionalBound});
AdditionalBound = "&", InterfaceType;
TypeArguments = "<", TypeArgumentList, ">";
TypeArgumentList = TypeArgument {",", TypeArgument};
TypeArgument = ReferenceType | Wildcard;
Wildcard = {Annotation}, "?", [WildcardBounds];
WildcardBounds = ("extends" | "super"), ReferenceType;
@endebnf

Names

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@startebnf
ModuleName = Identifier | ( ModuleName, ".", Identifier);
PackageName = Identifier | (PackageName, ".", Identifier);
TypeName = TypeIdentifier | (PackageOrTypeName, ".", TypeIdentifier);
ExpressionName = Identifier | ( AmbiguousName, ".", Identifier);
MethodName = UnqualifiedMethodIdentifier;
PackageOrTypeName = Identifier | (PackageOrTypeName, ".", Identifier);
AmbiguousName = Identifier | (AmbiguousName, ".", Identifier);
@endebnf

Classes

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@startebnf
ClassDeclaration = NormalClassDeclaration | EnumDeclaration | RecordDeclaration;
NormalClassDeclaration = {ClassModifier}, "class", TypeIdentifier, [TypeParameters], [ClassExtends], [ClassImplements], [ClassPermits], ClassBody;
ClassModifier = Annotation | "public" | "protected" | "private" | "abstract" | "static" | "final" | "sealed" | "non-sealed" | "strictfp";
TypeParameters = "<", TypeParameterList, ">";
TypeParameterList = TypeParameter, {",", TypeParameter};
ClassExtends = "extends", ClassType;
ClassImplements = "implements", InterfaceTypeList;
InterfaceTypeList = InterfaceType, {",", InterfaceType};
ClassPermits = "permits", TypeName, {",", TypeName};
ClassBody = "{", {ClassBodyDeclaration}, "}";
ClassBodyDeclaration = ClassMemberDeclaration | InstanceInitializer | StaticInitializer | ConstructorDeclaration;
ClassMemberDeclaration = (FieldDeclaration | MethodDeclaration | ClassDeclaration | InterfaceDeclaration), ";";
FieldDeclaration = {FieldModifier}, UnannType, VariableDeclaratorList, ";";
FieldModifier = Annotation | "public" | "protected" | "private" | "static" | "final" | "transient" | "volatile";
VariableDeclaratorList = VariableDeclarator, {",", VariableDeclarator};
VariableDeclarator = VariableDeclaratorId, ["=", VariableInitializer];
VariableDeclaratorId = Identifier, [Dims];
VariableInitializer = Expression | ArrayInitializer;
UnannType = UnannPrimitiveType | UnannReferenceType;
UnannPrimitiveType = NumericType | boolean;
UnannReferenceType = UnannClassOrInterfaceType | UnannTypeVariable | UnannArrayType;
UnannClassOrInterfaceType = UnannClassType | UnannInterfaceType;
UnannClassType = (TypeIdentifier, [TypeArguments]) | (PackageName, ".", {Annotation}, TypeIdentifier, [TypeArguments]) | (UnannClassOrInterfaceType, ".", {Annotation}, TypeIdentifier, [TypeArguments]) | (TypeIdentifier, [TypeArguments]) | (TypeIdentifier, [TypeArguments]);
UnannInterfaceType = UnannClassType;
UnannTypeVariable = TypeIdentifier;
UnannArrayType = (UnannPrimitiveType, Dims) | (UnannClassOrInterfaceType, Dims) | (UnannTypeVariable, Dims);
MethodDeclaration = {MethodModifier}, MethodHeader, MethodBody;
MethodModifier = Annotation | "public" | "protected" | "private" | "abstract" | "static" | "final" | "synchronized" | "native" | "strictfp";
MethodHeader = (Result, MethodDeclarator, [Throws]) | (TypeParameters, {Annotation}, Result, MethodDeclarator, [Throws]);
Result = UnannType | "void";
MethodDeclarator = Identifier, ( [ ReceiverParameter, "," ], [FormalParameterList] ), [Dims];
ReceiverParameter = {Annotation}, UnannType, [Identifier, "."], "this";
FormalParameterList = FormalParameter, {",", FormalParameter};
FormalParameter = ({VariableModifier}, UnannType, VariableDeclaratorId) | VariableArityParameter;
VariableArityParameter = {VariableModifier}, UnannType, {Annotation}, "...", Identifier;
VariableModifier = Annotation | "final";
Throws = "throws", ExceptionTypeList;
ExceptionTypeList = ExceptionType, {",", ExceptionType};
ExceptionType = ClassType | TypeVariable;
MethodBody = Block | ";";
InstanceInitializer = Block;
StaticInitializer = "static", Block;
ConstructorDeclaration = {ConstructorModifier}, ConstructorDeclarator, [Throws], ConstructorBody;
ConstructorModifier = Annotation | "public" | "protected" | "private";
ConstructorDeclarator = [TypeParameters], SimpleTypeName, ( [ReceiverParameter, ","], [FormalParameterList] );
SimpleTypeName = TypeIdentifier;
ConstructorBody = { [ExplicitConstructorInvocation], [BlockStatements] };
ExplicitConstructorInvocation = ( [TypeArguments], "this", "(", [ArgumentList], ")", ";" ) | ([TypeArguments], "super", "(", [ArgumentList], ")", ";" ) | (ExpressionName, ".", [TypeArguments], "super", "(", [ArgumentList], ")", ";" ) | (Primary, "." [TypeArguments], "super", "(" [ArgumentList], ")", ";";
EnumDeclaration = {ClassModifier}, "enum", TypeIdentifier, [ClassImplements], EnumBody;
EnumBody = "{", [EnumConstantList], [","], [EnumBodyDeclarations], "}";
EnumConstantList = EnumConstant, {",", EnumConstant};
EnumConstant = {EnumConstantModifier}, Identifier, ["(", [ArgumentList], ")"], [ClassBody];
EnumConstantModifier = Annotation;
EnumBodyDeclarations = ";", {ClassBodyDeclaration};
RecordDeclaration = {ClassModifier}, "record", TypeIdentifier, [TypeParameters], RecordHeader, [ClassImplements], RecordBody;
RecordHeader = "(", [RecordComponentList], ")";
RecordComponentList = RecordComponent, {",", RecordComponent};
RecordComponent = (RecordComponentModifier}, UnannType, Identifier) | VariableArityRecordComponent;
VariableArityRecordComponent = {RecordComponentModifier}, UnannType, {Annotation}, "...", Identifier;
RecordComponentModifier = Annotation;
RecordBody = "{", {RecordBodyDeclaration}, "}";
RecordBodyDeclaration = ClassBodyDeclaration | CompactConstructorDeclaration;
CompactConstructorDeclaration = {ConstructorModifier}, SimpleTypeName, ConstructorBody;
@endebnf

Interfaces

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@startebnf
InterfaceDeclaration = NormalInterfaceDeclaration | AnnotationInterfaceDeclaration;
NormalInterfaceDeclaration = {InterfaceModifier}, "interface", TypeIdentifier, [TypeParameters], [InterfaceExtends], [InterfacePermits], InterfaceBody;
InterfaceModifier = Annotation | "public" | "protected" | "private" | "abstract" | "static" | "sealed" | "non-sealed" | "strictfp";
InterfaceExtends = "extends", InterfaceTypeList;
InterfacePermits = "permits", TypeName, {",", TypeName};
InterfaceBody = "{", {InterfaceMemberDeclaration}, "}";
InterfaceMemberDeclaration = ConstantDeclaration | InterfaceMethodDeclaration | ClassDeclaration | InterfaceDeclaration | ";";
ConstantDeclaration = {ConstantModifier}, UnannType, VariableDeclaratorList, ";";
ConstantModifier = Annotation | "public" | "static" | "final";
InterfaceMethodDeclaration = {InterfaceMethodModifier}, MethodHeader, MethodBody;
InterfaceMethodModifier = Annotation | "public" | "private" | "abstract" | "default" | "static" | "strictfp";
AnnotationInterfaceDeclaration = {InterfaceModifier}, "@", "interface", TypeIdentifier, AnnotationInterfaceBody;
AnnotationInterfaceBody = "{", {AnnotationInterfaceMemberDeclaration}, "}";
AnnotationInterfaceMemberDeclaration = AnnotationInterfaceElementDeclaration | ConstantDeclaration | ClassDeclaration | InterfaceDeclaration, ";";
AnnotationInterfaceElementDeclaration = {AnnotationInterfaceElementModifier}, UnannType, Identifier, "(", ")", [Dims], [DefaultValue], ";";
AnnotationInterfaceElementModifier = Annotation | "public" | "abstract";
DefaultValue = "default", ElementValue;
Annotation = NormalAnnotation | MarkerAnnotation | SingleElementAnnotation;
NormalAnnotation = "@", TypeName, "(", [ElementValuePairList], ")";
ElementValuePairList = ElementValuePair, {",", ElementValuePair};
ElementValuePair = Identifier, "=", ElementValue;
ElementValue = ConditionalExpression | ElementValueArrayInitializer | Annotation;
ElementValueArrayInitializer = "{", [ElementValueList], [","], "}";
ElementValueList = ElementValue, {",", ElementValue};
MarkerAnnotation = "@", TypeName;
SingleElementAnnotation = "@", TypeName, "(", ElementValue, ")";
@endebnf

Arrays

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@startebnf
ArrayInitializer = "{", [VariableInitializerList], [","], "}";
VariableInitializerList = VariableInitializer, {",", VariableInitializer};
@endebnf

Blocks, Statements, and Patterns

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@startebnf
Block = "{", [BlockStatements], "}";
BlockStatements = BlockStatement, {BlockStatement};
BlockStatement = LocalClassOrInterfaceDeclaration | LocalVariableDeclarationStatement | Statement;
LocalClassOrInterfaceDeclaration = ClassDeclaration | NormalInterfaceDeclaration;
LocalVariableDeclarationStatement = LocalVariableDeclaration, ";";
LocalVariableDeclaration = {VariableModifier}, LocalVariableType, VariableDeclaratorList;
LocalVariableType = UnannType | "var";
Statement = StatementWithoutTrailingSubstatement | LabeledStatement | IfThenStatement | IfThenElseStatement | WhileStatement | ForStatement;
StatementNoShortIf = StatementWithoutTrailingSubstatement | LabeledStatementNoShortIf | IfThenElseStatementNoShortIf | WhileStatementNoShortIf | ForStatementNoShortIf;
StatementWithoutTrailingSubstatement = Block | EmptyStatement | ExpressionStatement | AssertStatement | SwitchStatement | DoStatement | BreakStatement | ContinueStatement | ReturnStatement | SynchronizedStatement | ThrowStatement | TryStatement | YieldStatement;
EmptyStatement = ";";
LabeledStatement = Identifier, ":", Statement;
LabeledStatementNoShortIf = Identifier, ":", StatementNoShortIf;
ExpressionStatement = StatementExpression, ";";
StatementExpression = Assignment | PreIncrementExpression | PreDecrementExpression | PostIncrementExpression | PostDecrementExpression | MethodInvocation | ClassInstanceCreationExpression;
IfThenStatement = "if", "(", Expression, ")", Statement;
IfThenElseStatement = "if", "(", Expression, ")", StatementNoShortIf, "else", Statement;
IfThenElseStatementNoShortIf = "if", "(", Expression, ")", StatementNoShortIf, "else", StatementNoShortIf;
AssertStatement = ("assert", Expression, ";") | ("assert", Expression, ":", Expression, ";");
SwitchStatement = "switch", "(", Expression, ")", SwitchBlock;
SwitchBlock = ( "{", SwitchRule, {SwitchRule}, "}" ) | ( "{", {SwitchBlockStatementGroup}, {SwitchLabel, ":"}, "}" );
SwitchRule = (SwitchLabel, "->", Expression, ";") |(SwitchLabel, "->", Block) | (SwitchLabel, "->", ThrowStatement);
SwitchBlockStatementGroup = SwitchLabel, ":", {SwitchLabel, ":"}, BlockStatements;
SwitchLabel = ("case", CaseConstant, {",", CaseConstant}) | "default";
CaseConstant = ConditionalExpression;
WhileStatement = "while", "(", Expression, ")", Statement;
WhileStatementNoShortIf = "while", "(", Expression, ")", StatementNoShortIf;
DoStatement = "do", Statement, "while", "(", Expression, ")", ";";
ForStatement = BasicForStatement | EnhancedForStatement | ForStatementNoShortIf | BasicForStatementNoShortIf | EnhancedForStatementNoShortIf;
BasicForStatement = "for", "(", [ForInit], ";", [Expression], ";", [ForUpdate], ")", Statement;
BasicForStatementNoShortIf = "for", "(", [ForInit], ";", [Expression], ";", [ForUpdate], ")", StatementNoShortIf;
ForInit = StatementExpressionList | LocalVariableDeclaration;
ForUpdate = StatementExpressionList;
StatementExpressionList = StatementExpression, {",", StatementExpression};
EnhancedForStatement = "for", "(", LocalVariableDeclaration, ":", Expression, ")", Statement;
EnhancedForStatementNoShortIf = "for", "(", LocalVariableDeclaration, ":", Expression, ")", StatementNoShortIf;
BreakStatement = break, [Identifier], ";";
YieldStatement = "yield", Expression, ";";
ContinueStatement = "continue", [Identifier], ";";
ReturnStatement = "return" [Expression], ";";
ThrowStatement = "throw", Expression, ";";
SynchronizedStatement = "synchronized", "(", Expression, ")", Block;
TryStatement = ("try", Block, Catches) | ("try", Block, [Catches], Finally ) | TryWithResourcesStatement;
Catches = CatchClause, {CatchClause};
CatchClause = "catch", "(", CatchFormalParameter, ")", Block;
CatchFormalParameter = {VariableModifier}, CatchType, VariableDeclaratorId;
CatchType = UnannClassType, {"|", ClassType};
Finally = "finally", Block;
TryWithResourcesStatement = "try", ResourceSpecification, Block, [Catches], [Finally];
ResourceSpecification = "(", ResourceList, [";"], ")";
ResourceList = Resource, {";", Resource};
Resource = LocalVariableDeclaration | VariableAccess;
Pattern = TypePattern;
TypePattern = LocalVariableDeclaration;

(* Expressions *)

Primary = PrimaryNoNewArray | ArrayCreationExpression;
PrimaryNoNewArray = Literal | ClassLiteral | "this" | (TypeName, ".", "this") | ( "(", Expression, ")" ) | ClassInstanceCreationExpression | FieldAccess | ArrayAccess | MethodInvocation | MethodReference;
ClassLiteral = (TypeName, { "[", "]" }, ".", "class") | (NumericType, {"[", "]"}, ".", "class") | ("boolean", {"[", "]"}, ".", "class") | ("void", ".", "class");
ClassInstanceCreationExpression = UnqualifiedClassInstanceCreationExpression | (ExpressionName, ".", UnqualifiedClassInstanceCreationExpression) |(Primary, ".", UnqualifiedClassInstanceCreationExpression);
UnqualifiedClassInstanceCreationExpression = "new", [TypeArguments], ClassOrInterfaceTypeToInstantiate, "(", [ArgumentList], ")", [ClassBody];
ClassOrInterfaceTypeToInstantiate = {Annotation}, Identifier, {".", {Annotation}, Identifier}, [TypeArgumentsOrDiamond];
TypeArgumentsOrDiamond = TypeArguments | ("<",">");
ArrayCreationExpression = ArrayCreationExpressionWithoutInitializer | ArrayCreationExpressionWithInitializer;
ArrayCreationExpressionWithoutInitializer = ("new", PrimitiveType, DimExprs, [Dims]) | ("new", ClassOrInterfaceType, DimExprs, [Dims]);
ArrayCreationExpressionWithInitializer = ("new", PrimitiveType, Dims, ArrayInitializer) | ("new", ClassOrInterfaceType, Dims, ArrayInitializer);
DimExprs = DimExpr, {DimExpr};
DimExpr = ({Annotation}, [ Expression ]) | (ArrayAccess, "=", ExpressionName, "[", Expression, "]") | (PrimaryNoNewArray, "[", Expression, "]") | (ArrayCreationExpressionWithInitializer, "[", Expression, "]");
FieldAccess = (Primary, ".", Identifier), ("super", ".", Identifier), (TypeName, ".", super, ".", Identifier);
MethodInvocation = (MethodName, "(", [ArgumentList], ")") | (TypeName, ".", [TypeArguments], Identifier, "(", [ArgumentList], ")") | (ExpressionName, ".", [TypeArguments], Identifier, "(", [ArgumentList], ")") | (Primary, ".", [TypeArguments], Identifier, "(", [ArgumentList], ")") | ("super", ".", [TypeArguments], Identifier, "(", [ArgumentList], ")") | (TypeName, ".", "super", ".", [TypeArguments], Identifier, "(", [ArgumentList], ")");
ArgumentList = Expression, {",", Expression};
MethodReference = (ExpressionName, "::", [TypeArguments], Identifier) | (Primary, "::", [TypeArguments], Identifier) | (ReferenceType, "::", [TypeArguments], Identifier) | ("super", "::", [TypeArguments], Identifier) | (TypeName, ".", super, "::", [TypeArguments], Identifier) | (ClassType, "::", [TypeArguments], "new") | (ArrayType, "::", "new");
Expression = LambdaExpression | AssignmentExpression;
LambdaExpression = LambdaParameters, "->", LambdaBody;
LambdaParameters = ("(", [LambdaParameterList], ")") | Identifier;
LambdaParameterList = (LambdaParameter, {",", LambdaParameter}) | (Identifier, {",", Identifier});
LambdaParameter = ({VariableModifier}, LambdaParameterType, VariableDeclaratorId) | VariableArityParameter;
LambdaParameterType = UnannType | "var";
LambdaBody = Expression | Block;
AssignmentExpression = ConditionalExpression | Assignment;
Assignment = LeftHandSide | AssignmentOperator | Expression;
LeftHandSide = ExpressionName | FieldAccess | ArrayAccess;
AssignmentOperator = "=" | "*=" | "/=" | "%=" | "+=" | "-=" | "<<=" | ">>=" | ">>>=" | "&=" | "^=" | "|=";
ConditionalExpression = ConditionalOrExpression | (ConditionalOrExpression, "?", Expression, ":", ConditionalExpression) | (ConditionalOrExpression, "?", Expression, ":", LambdaExpression);
ConditionalOrExpression = ConditionalAndExpression | (ConditionalOrExpression, "||", ConditionalAndExpression);
ConditionalAndExpression = InclusiveOrExpression | (ConditionalAndExpression, "&&", InclusiveOrExpression);
InclusiveOrExpression = ExclusiveOrExpression | (InclusiveOrExpression, "|", ExclusiveOrExpression);
ExclusiveOrExpression = AndExpression | (ExclusiveOrExpression, "^", AndExpression);
AndExpression = EqualityExpression, (AndExpression, "&", EqualityExpression) | (EqualityExpression, "=", RelationalExpression) | (EqualityExpression, "==", RelationalExpression) | (EqualityExpression, "!=", RelationalExpression);
RelationalExpression = ShiftExpression | (RelationalExpression, "<", ShiftExpression) | (RelationalExpression, ">", ShiftExpression) | (RelationalExpression, "<=", ShiftExpression) | (RelationalExpression, ">=", ShiftExpression) | (InstanceofExpression);
InstanceofExpression = (RelationalExpression, "instanceof", ReferenceType) | (RelationalExpression, "instanceof", Pattern);
ShiftExpression = AdditiveExpression | (ShiftExpression, "<<", AdditiveExpression) | (ShiftExpression, ">>", AdditiveExpression) | (ShiftExpression, ">>>", AdditiveExpression);
AdditiveExpression = MultiplicativeExpression | (AdditiveExpression, "+", MultiplicativeExpression) | (AdditiveExpression, "-", MultiplicativeExpression);
MultiplicativeExpression = UnaryExpression | (MultiplicativeExpression, "*", UnaryExpression) | (MultiplicativeExpression, "/", UnaryExpression) | (MultiplicativeExpression, "%", UnaryExpression);
UnaryExpression = PreIncrementExpression | PreDecrementExpression | ("+", UnaryExpression) | ("-", UnaryExpression) | UnaryExpressionNotPlusMinus;
PreIncrementExpression = "++", UnaryExpression;
PreDecrementExpression = "--", UnaryExpression;
UnaryExpressionNotPlusMinus = PostfixExpression | ("~", UnaryExpression) | ("!", UnaryExpression) | CastExpression | SwitchExpression;
PostfixExpression = Primary | ExpressionName | PostIncrementExpression | PostDecrementExpression;
PostIncrementExpression = PostfixExpression, "++";
PostDecrementExpression = PostfixExpression, "--";
CastExpression = ("(", PrimitiveType, ")", UnaryExpression) | ("(", ReferenceType, {AdditionalBound}, ")", UnaryExpressionNotPlusMinus) | ("(", ReferenceType, {AdditionalBound}, ")", LambdaExpression);
SwitchExpression = "switch", "(", Expression, ")", SwitchBlock;
ConstantExpression = Expression;
@endebnf

Remaining defects

Always observed on 2023-04-28

Could you put 'arrow head' on all rerouted lines?

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@startebnf
title Could you put 'arrow head' on all rerouted lines?
test = [1], [12], [123], [1234];
@endebnf

No Ref.

Order issue

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@startebnf
a = (one, two), three;
b = (one (* 1 *), two (* 2 *)), three (* 3 *);
@endebnf

[Ref. QA-17090]

Allow accentuated or Unicode char on EBNF meta-identifier or rule name.

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@startebnf
(* Test of accentuated or Unicode char*)
alt = été | hiver;
hiver = 'froid';
été = 'chaud';
@endebnf

[Ref. QA-17145]

Allow full restriction management with except-symbol "-"

🎉 Copied!

@startebnf
title First [modified] example of §5.8 Syntactic-term of ISO-EBNF

letter = ? "A" - "Z" ?;

vowel = "A" | "E" | "I" | "O" | "U";

consonant = letter - vowel;
@endebnf

[Ref. QA-16735]


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