XPath: Expr.

ParamList: Param, ( ',', Param )*.
Param: '$', EQName, TypeDeclaration?.
FunctionBody: EnclosedExpr.
EnclosedExpr: '{', Expr?, '}'.

Expr: ExprSingle, ( s?,',',s?, ExprSingle )*.

-ExprSingle: OrExpr; OrExprSingle.


-OrExprSingle: AndExpr.
OrExpr: AndExpr, (s?, 'or', s?,  AndExpr )+.
AndExpr: ComparisonExpr, (s?, 'and', s?, ComparisonExpr )*.
ComparisonExpr: StringConcatExpr, (s, ( @ValueComp ; @GeneralComp ;@ NodeComp ), s, StringConcatExpr )?.
StringConcatExpr: RangeExpr, (s?, '||', s?, RangeExpr )*.
RangeExpr: AdditiveExpr, ( s, 'to', s, AdditiveExpr )?.
AdditiveExpr: MultiplicativeExpr;
   MultiplicativeExpr,  s?, @AddOp, s?, AdditiveExpr.
@AddOp: ( '+' ; '-' ).
MultiplicativeExpr: UnionExpr;
   UnionExpr,  s?, @MultOp, s?, MultiplicativeExpr.
@MultOp:  '*' ; 'div' ; 'idiv' ; 'mod'.
UnionExpr: IntersectExceptExpr, ( ( 'union' ; '|' ), IntersectExceptExpr )*.
IntersectExceptExpr: InstanceofExpr, ( s, ( 'intersect' ;'except' ), s, InstanceofExpr )*.
InstanceofExpr: TreatExpr, ( s, 'instance', s, 'of', s, @SequenceType )?.
TreatExpr: CastExpr, ( s, -'treat', s, -'as', s, @SequenceType )?.
CastExpr: ArrowExpr, ( s, -'cast', s,-'as', s, @SingleType )?.
ArrowExpr: UnaryExpr, ( '=>', ArrowFunctionSpecifier, ArgumentList )*.


UnaryExpr: ( '-' ; '+' )*, ValueExpr.
-ValueExpr: SimpleMapExpr.
GeneralComp: '='; '!='; '<'; '<='; '>'; '>='.
ValueComp: 'eq'; 'ne'; 'lt'; 'le'; 'gt'; 'ge'.
NodeComp: 'is'; '<<'; '>>'.
SimpleMapExpr: PathExpr, ( '!', PathExpr )*.
PathExpr: '/', ( RelativePathExpr );
   '//', RelativePathExpr;
   RelativePathExpr.
RelativePathExpr: StepExpr, ( ( '/'; '//' ), StepExpr )*.

-StepExpr: PostfixExpr; AxisStep.
-AxisStep: ( ReverseStep;ForwardStep ).
ForwardStep: @ForwardAxis, NodeTest;
   AbbrevForwardStep.
ForwardAxis: 'child::';
   'descendant::';
   'attribute::';
   'self::';
   'descendant-or-self::';
   'following-sibling::';
   'following::';
   'namespace::'.
AbbrevForwardStep: '@'?, QName.
ReverseStep: @ReverseAxis, NodeTest;
   @AbbrevReverseStep.
ReverseAxis: 'parent::';
   'ancestor::';
   'preceding-sibling::';
   'preceding::';
   'ancestor-or-self::'.
AbbrevReverseStep: '..'.


-NodeTest:  KindTest; NameTest.
-NameTest: EQName; Wildcard.

PostfixExpr: PrimaryExpr.
ArgumentList: -'(',s?, ( -Argument,(s?,  -',', s?, -Argument )* )?, s?, -')'.

KeySpecifier: NCName;| IntegerLiteral; ParenthesizedExpr; '*'.
-ArrowFunctionSpecifier: EQName; VarRef; ParenthesizedExpr.

-PrimaryExpr: Literal;
   VarRef;
   ParenthesizedExpr;
   ContextItemExpr;
   FunctionCall;
   FunctionItemExpr;
   MapConstructor;
   ArrayConstructor;
   UnaryLookup.
-Literal: NumericLiteral; StringLiteral.
-NumericLiteral: IntegerLiteral; DecimalLiteral;| DoubleLiteral.
VarRef: -'$', @VarName.
VarName: EQName.
ParenthesizedExpr: -'(', Expr?, -')'.
ContextItemExpr: -'.'.
FunctionCall: @FunctionEQName, -ArgumentList.
-Argument: ExprSingle; ArgumentPlaceholder.
ArgumentPlaceholder: -'?'.
FunctionItemExpr: NamedFunctionRef; InlineFunctionExpr.
NamedFunctionRef: FunctionEQName, '#', IntegerLiteral.
InlineFunctionExpr: -'function', -'(', ParamList?, ')', ( s, 'as', s, SequenceType )?, FunctionBody.
MapConstructor: -'map', -'{', ( MapConstructorEntry, ( ',', MapConstructorEntry )* )?, -'}'.
MapConstructorEntry: MapKeyExpr, -':', MapValueExpr.
MapKeyExpr: ExprSingle.
MapValueExpr: ExprSingle.
ArrayConstructor: SquareArrayConstructor; CurlyArrayConstructor.
SquareArrayConstructor: -'[', ( ExprSingle, ( -',', ExprSingle )* )?, -']'.
CurlyArrayConstructor: -'array', '{', Expr?, -'}'.
UnaryLookup: -'?', KeySpecifier.

SingleType: SimpleTypeName, '?'?.
TypeDeclaration: 'as', SequenceType.
SequenceType: 'empty-sequence()';
   ItemType, OccurrenceIndicator?.
@OccurrenceIndicator: '?'; '*'; '+'.
ItemType: KindTest;
 'item()';
 FunctionTest;
 MapTest;
 ArrayTest;
 AtomicOrUnionType;
 ParenthesizedItemType.
AtomicOrUnionType: EQName.


-KindTest: DocumentTest;
   ElementTest;
   AttributeTest;
   SchemaElementTest;
   SchemaAttributeTest;
   PITest;
   CommentTest;
   TextTest;
   NamespaceNodeTest;
   AnyKindTest.
AnyKindTest: 'node()'.
DocumentTest: -'document-node(' , ( ElementTest ; SchemaElementTest )?, -')'.
TextTest: -'text()'.
CommentTest: -'comment()'.
NamespaceNodeTest: -'namespace-node()'.
PITest:  -'processing-instruction(' , ( NCName ; StringLiteral )?, -')'.
AttributeTest: -'attribute(' ,( AttribNameOrWildcard, ( ',', TypeName )? )?, -')'.
AttribNameOrWildcard: AttributeName; '*'.
SchemaAttributeTest: -'schema-attribute(', AttributeDeclaration, -')'.
AttributeDeclaration: AttributeName.
ElementTest: -'element(' , ( ElementNameOrWildcard, ( ',', TypeName, '?'? )? )?, -')'.
ElementNameOrWildcard: ElementName;'*'.
SchemaElementTest: -'schema-element(', ElementDeclaration, -')'.
ElementDeclaration: ElementName.

AttributeName: EQName.
ElementName: EQName.
SimpleTypeName: EQName.
TypeName: EQName.

FunctionTest: AnyFunctionTest; TypedFunctionTest.
AnyFunctionTest: -'function(*)'.
TypedFunctionTest: -'function(', ( SequenceType, ( -',', SequenceType )* )?, -')', s, 'as', s, SequenceType.
MapTest: AnyMapTest; TypedMapTest.
AnyMapTest: -'map(*)'.
TypedMapTest: -'map(', s, AtomicOrUnionType,s,  -',', s,  SequenceType, s, -')'.
ArrayTest: AnyArrayTest; TypedArrayTest.
AnyArrayTest: -'array(*)'.
TypedArrayTest: -'array(', s, SequenceType, s, -')'.
ParenthesizedItemType: -'(',s, ItemType,s, -')'.

FunctionEQName: FunctionName; URIQualifiedName.
EQName: QName; URIQualifiedName.

QName: FunctionName;
    'array';
    'attribute';
    'comment';
    'document-node';
    'element';
    'empty-sequence';
    'function';
    'if';
    'item';
    'map';
    'namespace-node';
    'node';
    'processing-instruction';
    'schema-attribute';
    'schema-element';
    'switch';
    'text';
    'typeswitch'.
 
 -FunctionName: QNameToken;
    'ancestor';
    'ancestor-or-self';
    'and';
    'cast';
    'castable';
    'child';
    'descendant';
    'descendant-or-self';
    'div';
    'else';
    'eq';
    'every';
    'except';
    'following';
    'following-sibling';
    'for';
    'ge';
    'gt';
    'idiv';
    'instance';
    'intersect';
    'is';
    'le';
    'let';
    'lt';
    'mod';
    'namespace';
    'ne';
    'or';
    'parent';
    'preceding';
    'preceding-sibling';
    'return';
    'satisfies';
    'self';
    'some';
    'to';
    'treat';
    'union'.

StringLiteral: -'"', ( EscapeQuot; ~['"'] )*, -'"';
   -"'", ( EscapeApos ; ~["'"] )*, -"'".
IntegerLiteral: -Digits.
DecimalLiteral: '.', -Digits;
   -Digits, '.', ['0'-'9']*.
DoubleLiteral: ( '.', -Digits ; -Digits, ( '.', ['0'-'9']* )? ), ['e'; 'E'], -Digits.

-URIQualifiedName: BracedURILiteral, NCName.
BracedURILiteral: 'Q', '{', ~['{';'}']*, '}'.
EscapeQuot: '""'.
EscapeApos: "''".

QNameToken: PrefixedName;  UnprefixedName.
PrefixedName: @Prefix, -':', @LocalPart.
UnprefixedName: LocalPart.
Prefix: NCName.
LocalPart: NCName.
NCName: @Name.

-NameStartChar: ['A'-'Z'];
   '_';
   ['a'-'z'].
-NameChar: NameStartChar;
   '-';
   '.';
   ['0'-'9'].  
Name: NameStartChar, NameChar*.
-s: -' '+.
Wildcard: '*';
   NCName, ':', '*';
   '*', ':', NCName;
   BracedURILiteral, '*'.
Digits: ['0'-'9']+.