Group:
	(BracketGroup | NonBracketGroup | Operand )
	(operators+=Operator '('* operands+=Operand 
	(operators+=Operator operands+=Operand) ')'*)*
	;

BracketGroup:
	'('NonBracketGroup')' (operators+=Operator operands+=Operand)+ 
;


NonBracketGroup:
	'('?
	operands+=Operand 
	(operators+=Operator operands+=Operand)+ ')'?

Value:
	STRING | '-'?INT | Decimal | Logical | DATA  
;

DATA: MONTH'/'DAY'/'YEAR;
DAY: INT;
MONTH: INT;
YEAR: INT;

DataType:
	'character' | 'integer' | 'decimal' | 'logical' | 'date'
;

Operator:
	'+' | '-' | '*' | '/' | 'MODULO' | EQ | '>'| '<' | '=>' | '=<' | '<>' | GroupOperator

Decision can match input such as "RULE_INT '/' RULE_INT '/' {RULE_INT, '.'..'FALSE'}" using multiple alternatives: 2, 5

grammar org.xtext.example.domainmodel.Domainmodel with org.eclipse.xtext.common.Terminals

generate domainmodel "http://www.xtext.org/example/domainmodel/Domainmodel"


ExpressionsModel:
	(statement+= Statement)*;
	
Statement:
	Definition | Assignment
;

Definition:
	'define' name=ID 'as' type=DataType; 
		
Assignment:
	left=Assignable EQ right=Expression 
;   

Assignable:
	def=[Definition|ID] 
;

Expression:
	 Group 
;

Group:
	(BracketGroup | NonBracketGroup | Operand )
	(operators+=Operator '('* operands+=Operand 
	(operators+=Operator operands+=Operand) ')'*)*
	;

BracketGroup:
	'('NonBracketGroup')' (operators+=Operator operands+=Operand)+ 
;


NonBracketGroup:
	'('?
	operands+=Operand 
	(operators+=Operator operands+=Operand)+ ')'?
;

Operand:
	Assignable | Value 
;

Value:
	STRING | '-'?INT | Decimal | Logical | DATA  
;

Decimal:
	'-'?INT?'.'INT
;

Logical:
	'TRUE' | 'FALSE'
;

DATA: DAY'/'MONTH'/'YEAR;
DAY: INT;
MONTH: INT;
YEAR: INT;

DataType:
	'character' | 'integer' | 'decimal' | 'logical' | 'date'
;

Operator:
	'+' | '-' | '*' | '/' | 'MODULO' | EQ | '>'| '<' | '=>' | '=<' | '<>' | GroupOperator
;


GroupOperator:
	'AND' | 'OR' | 'NOT'
;

terminal EQ:
	'='
;

Model:
	name=ID
	ass+=Assignment*
;

Assignment:
	name=ID "=" ex=Expression
;

Expression:
	->Date | Addition
;

Date returns Expression:
	a=INT "/" b=INT "/" c=INT
;
	
Addition returns Expression:
  Multiplication ({Addition.left=current} op=('+'|'-') right=Multiplication)*;
 
Multiplication returns Expression:
  Primary ({Multiplication.left=current} op=('*'|'/') right=Primary)*;
 
Primary returns Expression:
  NumberLiteral |
  '(' Expression ')';
 
NumberLiteral:
  value=INT;