function_declare returns [ASTNode node]:
	FUNCTION name=ID {
		List<String> paramIds = new ArrayList<>();
		List<ASTNode> body = new ArrayList<>();
	} PAR_OPEN ( id0=ID {
		paramIds.add($id0.text);
	} (COMMA id1=ID {
		paramIds.add($id1.text);
	} )* )? PAR_CLOSE BRACKET_OPEN ( sentence {
		body.add($sentence.node);
	} )*
	BRACKET_CLOSE{
		$node = new FunctionDeclare( $name.text , paramIds , body );
	};

function_ref returns [ASTNode node]:
	ID {
		List<ASTNode> params = new ArrayList<>();
	}
	PAR_OPEN ( e0=expression {
		params.add($e0.node);
	}(COMMA e1=expression {
		params.add($e1.node);
	})* )? PAR_CLOSE{
		$node = new FunctionRef( $ID.text , params );
	};