Clinical Quality Language Release 1 STU 4 (1.4)
This is the current officially released version of Clinical Quality Language, 1.4 in it's permanent home.
For a full list of available versions, see the Directory of published versions 
.
| Clinical Decision Support Work Group | Maturity Level: 4 | Standards Status: Trial Use |
This page contains the Antlr 4.0 grammar for Clinical Quality Language.
grammar cql;
/*
* Clinical Quality Language Grammar Specification
* Version 1.4 - STU4
*/
import fhirpath;
/*
* Parser Rules
*/
library
:
libraryDefinition?
usingDefinition*
includeDefinition*
codesystemDefinition*
valuesetDefinition*
codeDefinition*
conceptDefinition*
parameterDefinition*
statement*
EOF
;
/*
* Definitions
*/
libraryDefinition
: 'library' qualifiedIdentifier ('version' versionSpecifier)?
;
usingDefinition
: 'using' modelIdentifier ('version' versionSpecifier)?
;
includeDefinition
: 'include' qualifiedIdentifier ('version' versionSpecifier)? ('called' localIdentifier)?
;
localIdentifier
: identifier
;
accessModifier
: 'public'
| 'private'
;
parameterDefinition
: accessModifier? 'parameter' identifier (typeSpecifier)? ('default' expression)?
;
codesystemDefinition
: accessModifier? 'codesystem' identifier ':' codesystemId ('version' versionSpecifier)?
;
valuesetDefinition
: accessModifier? 'valueset' identifier ':' valuesetId ('version' versionSpecifier)? codesystems?
;
codesystems
: 'codesystems' '{' codesystemIdentifier (',' codesystemIdentifier)* '}'
;
codesystemIdentifier
: (libraryIdentifier '.')? identifier
;
libraryIdentifier
: identifier
;
codeDefinition
: accessModifier? 'code' identifier ':' codeId 'from' codesystemIdentifier displayClause?
;
conceptDefinition
: accessModifier? 'concept' identifier ':' '{' codeIdentifier (',' codeIdentifier)* '}' displayClause?
;
codeIdentifier
: (libraryIdentifier '.')? identifier
;
codesystemId
: STRING
;
valuesetId
: STRING
;
versionSpecifier
: STRING
;
codeId
: STRING
;
/*
* Type Specifiers
*/
typeSpecifier
: namedTypeSpecifier
| listTypeSpecifier
| intervalTypeSpecifier
| tupleTypeSpecifier
| choiceTypeSpecifier
;
namedTypeSpecifier
: (qualifier '.')* referentialOrTypeNameIdentifier
;
modelIdentifier
: identifier
;
listTypeSpecifier
: 'List' '<' typeSpecifier '>'
;
intervalTypeSpecifier
: 'Interval' '<' typeSpecifier '>'
;
tupleTypeSpecifier
: 'Tuple' '{' tupleElementDefinition (',' tupleElementDefinition)* '}'
;
tupleElementDefinition
: referentialIdentifier typeSpecifier
;
choiceTypeSpecifier
: 'Choice' '<' typeSpecifier (',' typeSpecifier)* '>'
;
/*
* Statements
*/
statement
: expressionDefinition
| contextDefinition
| functionDefinition
;
expressionDefinition
: 'define' accessModifier? identifier ':' expression
;
contextDefinition
: 'context' (modelIdentifier '.')? identifier
;
functionDefinition
: 'define' accessModifier? 'function' identifierOrFunctionIdentifier '(' (operandDefinition (',' operandDefinition)*)? ')'
('returns' typeSpecifier)?
':' (functionBody | 'external')
;
operandDefinition
: referentialIdentifier typeSpecifier
;
functionBody
: expression
;
/*
* Expressions
*/
querySource
: retrieve
| qualifiedIdentifierExpression
| '(' expression ')'
;
aliasedQuerySource
: querySource alias
;
alias
: identifier
;
queryInclusionClause
: withClause
| withoutClause
;
withClause
: 'with' aliasedQuerySource 'such that' expression
;
withoutClause
: 'without' aliasedQuerySource 'such that' expression
;
retrieve
: '[' (contextIdentifier '->')? namedTypeSpecifier (':' (codePath 'in')? terminology)? ']'
;
contextIdentifier
: qualifiedIdentifierExpression
;
codePath
: simplePath
;
terminology
: qualifiedIdentifierExpression
| expression
;
qualifier
: identifier
;
query
: sourceClause letClause? queryInclusionClause* whereClause? returnClause? sortClause?
;
sourceClause
: 'from'? aliasedQuerySource (',' aliasedQuerySource)*
;
letClause
: 'let' letClauseItem (',' letClauseItem)*
;
letClauseItem
: identifier ':' expression
;
whereClause
: 'where' expression
;
returnClause
: 'return' ('all' | 'distinct')? expression
;
sortClause
: 'sort' ( sortDirection | ('by' sortByItem (',' sortByItem)*) )
;
sortDirection
: 'asc' | 'ascending'
| 'desc' | 'descending'
;
sortByItem
: expressionTerm sortDirection?
;
qualifiedIdentifier
: (qualifier '.')* identifier
;
qualifiedIdentifierExpression
: (qualifierExpression '.')* referentialIdentifier
;
qualifierExpression
: referentialIdentifier
;
simplePath
: referentialIdentifier #simplePathReferentialIdentifier
| simplePath '.' referentialIdentifier #simplePathQualifiedIdentifier
| simplePath '[' simpleLiteral ']' #simplePathIndexer
;
simpleLiteral
: STRING
| NUMBER
;
expression
: expressionTerm #termExpression
| retrieve #retrieveExpression
| query #queryExpression
| expression 'is' 'not'? ('null' | 'true' | 'false') #booleanExpression
| expression ('is' | 'as') typeSpecifier #typeExpression
| 'cast' expression 'as' typeSpecifier #castExpression
| 'not' expression #notExpression
| 'exists' expression #existenceExpression
| expression 'properly'? 'between' expressionTerm 'and' expressionTerm #betweenExpression
| ('duration' 'in')? pluralDateTimePrecision 'between' expressionTerm 'and' expressionTerm #durationBetweenExpression
| 'difference' 'in' pluralDateTimePrecision 'between' expressionTerm 'and' expressionTerm #differenceBetweenExpression
| expression ('<=' | '<' | '>' | '>=') expression #inequalityExpression
| expression intervalOperatorPhrase expression #timingExpression
| expression ('=' | '!=' | '~' | '!~') expression #equalityExpression
| expression ('in' | 'contains') dateTimePrecisionSpecifier? expression #membershipExpression
| expression 'and' expression #andExpression
| expression ('or' | 'xor') expression #orExpression
| expression 'implies' expression #impliesExpression
| expression ('|' | 'union' | 'intersect' | 'except') expression #inFixSetExpression
;
dateTimePrecision
: 'year' | 'month' | 'week' | 'day' | 'hour' | 'minute' | 'second' | 'millisecond'
;
dateTimeComponent
: dateTimePrecision
| 'date'
| 'time'
| 'timezoneoffset'
;
pluralDateTimePrecision
: 'years' | 'months' | 'weeks' | 'days' | 'hours' | 'minutes' | 'seconds' | 'milliseconds'
;
expressionTerm
: term #termExpressionTerm
| expressionTerm '.' qualifiedInvocation #invocationExpressionTerm
| expressionTerm '[' expression ']' #indexedExpressionTerm
| 'convert' expression 'to' (typeSpecifier | unit) #conversionExpressionTerm
| ('+' | '-') expressionTerm #polarityExpressionTerm
| ('start' | 'end') 'of' expressionTerm #timeBoundaryExpressionTerm
| dateTimeComponent 'from' expressionTerm #timeUnitExpressionTerm
| 'duration' 'in' pluralDateTimePrecision 'of' expressionTerm #durationExpressionTerm
| 'difference' 'in' pluralDateTimePrecision 'of' expressionTerm #differenceExpressionTerm
| 'width' 'of' expressionTerm #widthExpressionTerm
| 'successor' 'of' expressionTerm #successorExpressionTerm
| 'predecessor' 'of' expressionTerm #predecessorExpressionTerm
| 'singleton' 'from' expressionTerm #elementExtractorExpressionTerm
| 'point' 'from' expressionTerm #pointExtractorExpressionTerm
| ('minimum' | 'maximum') namedTypeSpecifier #typeExtentExpressionTerm
| expressionTerm '^' expressionTerm #powerExpressionTerm
| expressionTerm ('*' | '/' | 'div' | 'mod') expressionTerm #multiplicationExpressionTerm
| expressionTerm ('+' | '-' | '&') expressionTerm #additionExpressionTerm
| 'if' expression 'then' expression 'else' expression #ifThenElseExpressionTerm
| 'case' expression? caseExpressionItem+ 'else' expression 'end' #caseExpressionTerm
| ('distinct' | 'flatten') expression #aggregateExpressionTerm
| ('expand' | 'collapse') expression ('per' (dateTimePrecision | expression))? #setAggregateExpressionTerm
;
caseExpressionItem
: 'when' expression 'then' expression
;
dateTimePrecisionSpecifier
: dateTimePrecision 'of'
;
relativeQualifier
: 'or before'
| 'or after'
;
offsetRelativeQualifier
: 'or more'
| 'or less'
;
exclusiveRelativeQualifier
: 'less than'
| 'more than'
;
quantityOffset
: (quantity offsetRelativeQualifier?)
| (exclusiveRelativeQualifier quantity)
;
temporalRelationship
: ('on or'? ('before' | 'after'))
| (('before' | 'after') 'or on'?)
;
intervalOperatorPhrase
: ('starts' | 'ends' | 'occurs')? 'same' dateTimePrecision? (relativeQualifier | 'as') ('start' | 'end')? #concurrentWithIntervalOperatorPhrase
| 'properly'? 'includes' dateTimePrecisionSpecifier? ('start' | 'end')? #includesIntervalOperatorPhrase
| ('starts' | 'ends' | 'occurs')? 'properly'? ('during' | 'included in') dateTimePrecisionSpecifier? #includedInIntervalOperatorPhrase
| ('starts' | 'ends' | 'occurs')? quantityOffset? temporalRelationship dateTimePrecisionSpecifier? ('start' | 'end')? #beforeOrAfterIntervalOperatorPhrase
| ('starts' | 'ends' | 'occurs')? 'properly'? 'within' quantity 'of' ('start' | 'end')? #withinIntervalOperatorPhrase
| 'meets' ('before' | 'after')? dateTimePrecisionSpecifier? #meetsIntervalOperatorPhrase
| 'overlaps' ('before' | 'after')? dateTimePrecisionSpecifier? #overlapsIntervalOperatorPhrase
| 'starts' dateTimePrecisionSpecifier? #startsIntervalOperatorPhrase
| 'ends' dateTimePrecisionSpecifier? #endsIntervalOperatorPhrase
;
term
: invocation #invocationTerm
| literal #literalTerm
| externalConstant #externalConstantTerm
| intervalSelector #intervalSelectorTerm
| tupleSelector #tupleSelectorTerm
| instanceSelector #instanceSelectorTerm
| listSelector #listSelectorTerm
| codeSelector #codeSelectorTerm
| conceptSelector #conceptSelectorTerm
| '(' expression ')' #parenthesizedTerm
;
qualifiedInvocation // Terms that can be used after the function/member invocation '.'
: referentialIdentifier #qualifiedMemberInvocation
| qualifiedFunction #qualifiedFunctionInvocation
;
qualifiedFunction
: identifierOrFunctionIdentifier '(' paramList? ')'
;
invocation
: referentialIdentifier #memberInvocation
| function #functionInvocation
| '$this' #thisInvocation
| '$index' #indexInvocation
| '$total' #totalInvocation
;
function
: referentialIdentifier '(' paramList? ')'
;
ratio
: quantity ':' quantity
;
literal
: ('true' | 'false') #booleanLiteral
| 'null' #nullLiteral
| STRING #stringLiteral
| NUMBER #numberLiteral
| DATETIME #dateTimeLiteral
| TIME #timeLiteral
| quantity #quantityLiteral
| ratio #ratioLiteral
;
intervalSelector
: // TODO: Consider this as an alternative syntax for intervals... (would need to be moved up to expression to make it work)
//expression ( '..' | '*.' | '.*' | '**' ) expression;
'Interval' ('['|'(') expression ',' expression (']'|')')
;
tupleSelector
: 'Tuple'? '{' (':' | (tupleElementSelector (',' tupleElementSelector)*)) '}'
;
tupleElementSelector
: referentialIdentifier ':' expression
;
instanceSelector
: namedTypeSpecifier '{' (':' | (instanceElementSelector (',' instanceElementSelector)*)) '}'
;
instanceElementSelector
: referentialIdentifier ':' expression
;
listSelector
: ('List' ('<' typeSpecifier '>')?)? '{' (expression (',' expression)*)? '}'
;
displayClause
: 'display' STRING
;
codeSelector
: 'Code' STRING 'from' codesystemIdentifier displayClause?
;
conceptSelector
: 'Concept' '{' codeSelector (',' codeSelector)* '}' displayClause?
;
keyword
: 'after'
| 'all'
| 'and'
| 'as'
| 'asc'
| 'ascending'
| 'before'
| 'between'
| 'by'
| 'called'
| 'case'
| 'cast'
| 'code'
| 'Code'
| 'codesystem'
| 'codesystems'
| 'collapse'
| 'concept'
| 'Concept'
| 'contains'
| 'context'
| 'convert'
| 'date'
| 'day'
| 'days'
| 'default'
| 'define'
| 'desc'
| 'descending'
| 'difference'
| 'display'
| 'distinct'
| 'div'
| 'duration'
| 'during'
| 'else'
| 'end'
| 'ends'
| 'except'
| 'exists'
| 'expand'
| 'false'
| 'flatten'
| 'from'
| 'function'
| 'hour'
| 'hours'
| 'if'
| 'implies'
| 'in'
| 'include'
| 'includes'
| 'included in'
| 'intersect'
| 'Interval'
| 'is'
| 'let'
| 'library'
| 'List'
| 'maximum'
| 'meets'
| 'millisecond'
| 'milliseconds'
| 'minimum'
| 'minute'
| 'minutes'
| 'mod'
| 'month'
| 'months'
| 'not'
| 'null'
| 'occurs'
| 'of'
| 'on or'
| 'or'
| 'or after'
| 'or before'
| 'or less'
| 'or more'
| 'or on'
| 'overlaps'
| 'parameter'
| 'per'
| 'predecessor'
| 'private'
| 'properly'
| 'public'
| 'return'
| 'same'
| 'second'
| 'seconds'
| 'singleton'
| 'start'
| 'starts'
| 'sort'
| 'successor'
| 'such that'
| 'then'
| 'time'
| 'timezoneoffset'
| 'to'
| 'true'
| 'Tuple'
| 'union'
| 'using'
| 'valueset'
| 'version'
| 'week'
| 'weeks'
| 'where'
| 'when'
| 'width'
| 'with'
| 'within'
| 'without'
| 'xor'
| 'year'
| 'years'
;
// NOTE: Not used, this is the set of reserved words that may not appear as identifiers in ambiguous contexts
reservedWord
: 'all'
| 'and'
| 'as'
| 'after'
| 'before'
| 'between'
| 'case'
| 'cast'
| 'Code'
| 'collapse'
| 'Concept'
| 'convert'
| 'day'
| 'days'
| 'difference'
| 'distinct'
| 'duration'
| 'during'
| 'else'
| 'exists'
| 'expand'
| 'false'
| 'flatten'
| 'from'
| 'if'
| 'in'
| 'included in'
| 'is'
| 'hour'
| 'hours'
| 'Interval'
| 'let'
| 'List'
| 'maximum'
| 'millisecond'
| 'milliseconds'
| 'minimum'
| 'minute'
| 'minutes'
| 'month'
| 'months'
| 'not'
| 'null'
| 'occurs'
| 'of'
| 'on or'
| 'or'
| 'or on'
| 'per'
| 'properly'
| 'return'
| 'same'
| 'second'
| 'seconds'
| 'singleton'
| 'sort'
| 'such that'
| 'then'
| 'to'
| 'true'
| 'Tuple'
| 'week'
| 'weeks'
| 'when'
| 'with'
| 'within'
| 'without'
| 'year'
| 'years'
;
// Keyword identifiers are keywords that may be used as identifiers in a referential context
// Effectively, keyword except reservedWord
keywordIdentifier
: 'asc'
| 'ascending'
| 'by'
| 'called'
| 'code'
| 'codesystem'
| 'codesystems'
| 'concept'
| 'contains'
| 'context'
| 'date'
| 'default'
| 'define'
| 'desc'
| 'descending'
| 'display'
| 'div'
| 'end'
| 'ends'
| 'except'
| 'function'
| 'implies'
| 'include'
| 'includes'
| 'intersect'
| 'library'
| 'meets'
| 'mod'
| 'or after'
| 'or before'
| 'or less'
| 'or more'
| 'overlaps'
| 'parameter'
| 'predecessor'
| 'private'
| 'public'
| 'start'
| 'starts'
| 'successor'
| 'time'
| 'timezoneoffset'
| 'union'
| 'using'
| 'valueset'
| 'version'
| 'where'
| 'width'
| 'xor'
;
// Obsolete identifiers are keywords that could be used as identifiers in CQL 1.3
// NOTE: Not currently used, this is the set of keywords that were defined as allowed identifiers as part of 1.3
// NOTE: Several keywords were commented out in this list (notably exists) because of an issue with the ANTLR tooling.
// In 4.5, having these keywords as identifiers results in unacceptable parsing performance. In 4.6+, having them as
// identifiers resulted in incorrect parsing. See Github issue [#343](https://github.com/cqframework/clinical_quality_language/issues/343) for more detail
// This should no longer be an issue with 1.4 due to the introduction of reserved words
obsoleteIdentifier
: 'all'
| 'Code'
| 'code'
| 'Concept'
| 'concept'
| 'contains'
| 'date'
| 'display'
| 'distinct'
| 'end'
| 'exists'
| 'not'
| 'start'
| 'time'
| 'timezoneoffset'
| 'version'
| 'where'
;
// Function identifiers are keywords that may be used as identifiers for functions
functionIdentifier
: 'after'
| 'all'
| 'and'
| 'as'
| 'asc'
| 'ascending'
| 'before'
| 'between'
| 'by'
| 'called'
| 'case'
| 'cast'
| 'code'
| 'Code'
| 'codesystem'
| 'codesystems'
| 'collapse'
| 'concept'
| 'Concept'
| 'contains'
| 'context'
| 'convert'
| 'date'
| 'day'
| 'days'
| 'default'
| 'define'
| 'desc'
| 'descending'
| 'difference'
| 'display'
| 'distinct'
| 'div'
| 'duration'
| 'during'
| 'else'
| 'end'
| 'ends'
| 'except'
| 'exists'
| 'expand'
| 'false'
| 'flatten'
| 'from'
| 'function'
| 'hour'
| 'hours'
| 'if'
| 'implies'
| 'in'
| 'include'
| 'includes'
| 'included in'
| 'intersect'
| 'Interval'
| 'is'
| 'let'
| 'library'
| 'List'
| 'maximum'
| 'meets'
| 'millisecond'
| 'milliseconds'
| 'minimum'
| 'minute'
| 'minutes'
| 'mod'
| 'month'
| 'months'
| 'not'
| 'null'
| 'occurs'
| 'of'
| 'or'
| 'or after'
| 'or before'
| 'or less'
| 'or more'
| 'overlaps'
| 'parameter'
| 'per'
| 'predecessor'
| 'private'
| 'properly'
| 'public'
| 'return'
| 'same'
| 'singleton'
| 'second'
| 'seconds'
| 'start'
| 'starts'
| 'sort'
| 'successor'
| 'such that'
| 'then'
| 'time'
| 'timezoneoffset'
| 'to'
| 'true'
| 'Tuple'
| 'union'
| 'using'
| 'valueset'
| 'version'
| 'week'
| 'weeks'
| 'where'
| 'when'
| 'width'
| 'with'
| 'within'
| 'without'
| 'xor'
| 'year'
| 'years'
;
// Reserved words that are also type names
typeNameIdentifier
: 'Code'
| 'Concept'
| 'date'
| 'time'
;
referentialIdentifier
: identifier
| keywordIdentifier
;
referentialOrTypeNameIdentifier
: referentialIdentifier
| typeNameIdentifier
;
identifierOrFunctionIdentifier
: identifier
| functionIdentifier
;
identifier
: IDENTIFIER
| DELIMITEDIDENTIFIER
| QUOTEDIDENTIFIER
;
QUOTEDIDENTIFIER
: '"' (ESC | .)*? '"'
;
fragment ESC
: '\\' ([`'"\\/fnrt] | UNICODE) // allow \`, \', \", \\, \/, \f, etc. and \uXXX
;
NOTE: CQL extends from the FHIRPath grammar, and so uses the core production rules defined there. The FHIRPath grammar is included here for reference only, the FHIRPath grammar below is part of the FHIRPath specification. —-
grammar fhirpath;
// Grammar rules
// [FHIRPath](http://hl7.org/fhirpath/2019May) Normative Ballot 3
//prog: line (line)*;
//line: ID ( '(' expr ')') ':' expr '\r'? '\n';
expression
: term #termExpression
| expression '.' invocation #invocationExpression
| expression '[' expression ']' #indexerExpression
| ('+' | '-') expression #polarityExpression
| expression ('*' | '/' | 'div' | 'mod') expression #multiplicativeExpression
| expression ('+' | '-' | '&') expression #additiveExpression
| expression ('is' | 'as') typeSpecifier #typeExpression
| expression '|' expression #unionExpression
| expression ('<=' | '<' | '>' | '>=') expression #inequalityExpression
| expression ('=' | '~' | '!=' | '!~') expression #equalityExpression
| expression ('in' | 'contains') expression #membershipExpression
| expression 'and' expression #andExpression
| expression ('or' | 'xor') expression #orExpression
| expression 'implies' expression #impliesExpression
//| (IDENTIFIER)? '=>' expression #lambdaExpression
;
term
: invocation #invocationTerm
| literal #literalTerm
| externalConstant #externalConstantTerm
| '(' expression ')' #parenthesizedTerm
;
literal
: '{' '}' #nullLiteral
| ('true' | 'false') #booleanLiteral
| STRING #stringLiteral
| NUMBER #numberLiteral
| DATETIME #dateTimeLiteral
| TIME #timeLiteral
| quantity #quantityLiteral
;
externalConstant
: '%' ( identifier | STRING )
;
invocation // Terms that can be used after the function/member invocation '.'
: identifier #memberInvocation
| function #functionInvocation
| '$this' #thisInvocation
| '$index' #indexInvocation
| '$total' #totalInvocation
;
function
: identifier '(' paramList? ')'
;
paramList
: expression (',' expression)*
;
quantity
: NUMBER unit?
;
unit
: dateTimePrecision
| pluralDateTimePrecision
| STRING // UCUM syntax for units of measure
;
dateTimePrecision
: 'year' | 'month' | 'week' | 'day' | 'hour' | 'minute' | 'second' | 'millisecond'
;
pluralDateTimePrecision
: 'years' | 'months' | 'weeks' | 'days' | 'hours' | 'minutes' | 'seconds' | 'milliseconds'
;
typeSpecifier
: qualifiedIdentifier
;
qualifiedIdentifier
: identifier ('.' identifier)*
;
identifier
: IDENTIFIER
| DELIMITEDIDENTIFIER
| 'as'
| 'contains'
| 'in'
| 'is'
;
/****************************************************************
Lexical rules
*****************************************************************/
// Not sure why, but with these as lexical rules, when the grammar is imported into CQL, they are not correctly recognized
// Moving the same rules into the literal production rule above corrects the issue
//EMPTY
// : '{' '}'
// ; // To create an empty array (and avoid a NULL literal)
//BOOL
// : 'true'
// | 'false'
// ;
DATETIME
: '@'
[0-9][0-9][0-9][0-9] // year
(
(
'-'[0-9][0-9] // month
(
(
'-'[0-9][0-9] // day
('T' TIMEFORMAT?)?
)
| 'T'
)?
)
| 'T'
)?
('Z' | ('+' | '-') [0-9][0-9]':'[0-9][0-9])? // timezoneOffset
;
TIME
: '@' 'T' TIMEFORMAT
;
fragment TIMEFORMAT
: [0-9][0-9] (':'[0-9][0-9] (':'[0-9][0-9] ('.'[0-9]+)?)?)?
;
IDENTIFIER
: ([A-Za-z] | '_')([A-Za-z0-9] | '_')* // Added _ to support CQL (FHIR could constrain it out)
;
DELIMITEDIDENTIFIER
: '`' (ESC | .)*? '`'
;
STRING
: '\'' (ESC | .)*? '\''
;
// Also allows leading zeroes now (just like CQL and XSD)
NUMBER
: [0-9]+('.' [0-9]+)?
;
// Pipe whitespace to the HIDDEN channel to support retrieving source text through the parser.
WS
: [ \r\n\t]+ -> channel(HIDDEN)
;
COMMENT
: '/*' .*? '*/' -> channel(HIDDEN)
;
LINE_COMMENT
: '//' ~[\r\n]* -> channel(HIDDEN)
;
fragment ESC
: '\\' ([`'\\/fnrt] | UNICODE) // allow \`, \', \\, \/, \f, etc. and \uXXX
;
fragment UNICODE
: 'u' HEX HEX HEX HEX
;
fragment HEX
: [0-9a-fA-F]
;