Package net.ssehub.easy.varModel.cstEvaluation

Class EvaluationAccessor

  • Direct Known Subclasses:
    AbstractDecisionVariableEvaluationAccessor, ConstantAccessor
    public abstract class EvaluationAccessor
extends java.lang.Object
    Defines a unified accessor to variables, constants, slots etc. Please note that individual implementations shall be accessible via pools. Also records nested variables as evaluation context, e.g., to carry variables over a container aggregation function and to allow access to slots/attributes in following expressions. [public for testing]
    Author:
    Holger Eichelberger

    • Constructor Detail

      • EvaluationAccessor

        public EvaluationAccessor()

    • Method Detail

      • bind

        protected void bind​(EvaluationContext context)
        Binds the accessor to the given context.
        Parameters:
        context - the context to bind the accessor to
        See Also:
        clear()

      • clear

        public void clear()
        Clears the accessor for reuse.

      • getContext

        public EvaluationContext getContext()
        Returns the evaluation context.
        Returns:
        the evaluation context

      • getValue

        public abstract Value getValue()
        Returns the value of the accessed element.
        Returns:
        the value (may be null if undefined)

      • getDereferencedValue

        public Value getDereferencedValue()
        Returns the value of the accessed element, referred values are dereferenced.
        Note: This method is expensive as it may create a new EvaluationVisitor to resolve reference expressions.
        Returns:
        the dereferenced value (may be null if undefined)
        See Also:
        getValue()

      • getReferenceValue

        public abstract Value getReferenceValue()
        Returns the value of a reference to the accessed element.
        Returns:
        the value (may be null if undefined)

      • setValue

        public abstract boolean setValue​(Value value,
                                 boolean asAssignment)
        Defines a new value for the accessed element. In case of failures, add appropriate messages to the context.
        Parameters:
        value - the new value
        asAssignment - does this happen through an IVML assignment operation
        Returns:
        true if successful, false else

      • getValue

        public EvaluationAccessor getValue​(EvaluationAccessor accessor)
        Returns a nested value based on the given accessor.
        Parameters:
        accessor - the accessor to determine the nested value
        Returns:
        the nested value

      • setValue

        public void setValue​(EvaluationAccessor accessor,
                     Value value)
        Changes a nested value based on the given accessor.
        Parameters:
        accessor - the accessor to determine the nested value
        value - the new nested value

      • isAssigned

        public boolean isAssigned()
        Returns whether the underlying value is assigned or still undefined.
        Returns:
        true if a value is assigned, false else

      • release

        public abstract void release()
        Releases this instance.

      • getVariable

        public abstract IDecisionVariable getVariable()
        Returns the underlying variable.
        Returns:
        the underlying variable (may be null)

      • release

        public static <T extends EvaluationAccessor> T release​(T accessor)
        Releases the given accessor.
        Type Parameters:
        T - the type of the accessor
        Parameters:
        accessor - the accessor to be released (may be null)
        Returns:
        always null (to ease clearing local variables)

      • isAssignable

        public abstract boolean isAssignable()
        Returns whether values can be assigned to this evaluator.
        Returns:
        true if values can be assigned, false else

      • validateContext

        public void validateContext​(EvaluationContext context)
        Validates the context and sets the contained context to context if not given.
        Parameters:
        context - the context to validate with

      • dereferenceIfNeeded

        protected IDecisionVariable dereferenceIfNeeded​(IDecisionVariable variable,
                                                Value value)
        Dereferences variable if of reference type and value is not of reference type.
        Parameters:
        variable - the variable
        value - the value to consider
        Returns:
        variable or the dereferenced variable

      • bindContainer

        public void bindContainer​(IDecisionVariable container)
        Binds a container as provider for nested variables against this accessor in order to carry information about the underlying variables as long as possible through the evaluation.
        Parameters:
        container - the

      • addBoundContainerElement

        public void addBoundContainerElement​(EvaluationAccessor accessor,
                                     int index)
        Adds the bound container element stored at index in accessor to this accessor. If the bound container element does not exist, null will be added.
        Parameters:
        accessor - the accessor to take the bound container element from
        index - the index

      • clearContainerElements

        public void clearContainerElements()
        Clears the bound container elements.

      • addBoundContainerElement

        public void addBoundContainerElement​(IDecisionVariable element)
        Adds element to the bound container elements.
        Parameters:
        element - the element to add (may be null for none

      • bindContainer

        public void bindContainer​(EvaluationAccessor accessor)
        Binds all bound container elements stored in accessor to this accessor. Clears already bound elements in this accessor.
        Parameters:
        accessor - the accessor to take the elements from

      • getBoundContainerElement

        public IDecisionVariable getBoundContainerElement​(int index)
        Returns a container element. This method intentionally does not throw the typical exceptions.
        Parameters:
        index - the 0-based index
        Returns:
        the element or null if it does not exist/is stored.

      • getBoundContainerElementCount

        public int getBoundContainerElementCount()
        Returns the number of container elements.
        Returns:
        the number of container elements

      • isConstant

        public boolean isConstant()
        Returns whether this accessor represents a constant in the sense of the evaluation process, i.e., a value that is already evaluated to its very end and not linked to any decision variable.
        Returns:
        true for constant, false else