Class Expression

    • Field Detail

      • rule

        protected Rule rule
      • type

        protected Type type
      • charPos

        protected int charPos
      • line

        protected int line
    • Constructor Detail

      • Expression

        protected Expression​(Rule rule,
                             Type type,
                             ParseNode token)
        Create a new expression.
        Parameters:
        rule - the rule for this expression
        type - the type for this expression
        token - the token for this expression
    • Method Detail

      • bind

        public abstract void bind()
                           throws TypeException
        verify that variables mentioned in this expression are actually available in the rule bindings list
        Throws:
        TypeException - if any variable is missing or has the wrong type
      • getPos

        public String getPos()
      • getType

        public Type getType()
      • typeCheck

        public abstract Type typeCheck​(Type expected)
                                throws TypeException
        ensure that all type references in the expression and its component expressions can be resolved, that the type of the expression is well-defined and that it is compatible with the type expected in the context in which it occurs.
        Specified by:
        typeCheck in class RuleElement
        Parameters:
        expected - the type expected for the expression in the contxet in which it occurs. this may be void but should not be undefined at the point where type checking is performed.
        Returns:
        the type of the expression
        Throws:
        TypeException - if a type check failure occurs
      • interpret

        public abstract Object interpret​(HelperAdapter helper)
                                  throws ExecuteException
        evaluate the expression by interpreting the expression tree
        Specified by:
        interpret in class RuleElement
        Parameters:
        helper - an execution context associated with the rule which contains a map of current bindings for rule variables and another map of their declared types both of which are indexed by variable name. This includes entries for the helper (name "-1"), the recipient if the trigger method is not static (name "0") and the trigger method arguments (names "1", ...)
        Returns:
        the result of evaluation as an Object
        Throws:
        ExecuteException - if an error occurs during execution