Package ptolemy.actor.gt

Class Constraint

  • All Implemented Interfaces:
    java.lang.Cloneable, HasTypeConstraints, Typeable, Changeable, Debuggable, DebugListener, Derivable, ModelErrorHandler, MoMLExportable, Moveable, Nameable, Settable, ValueListener
    public class Constraint
extends GTParameter
    Constraint used to restrict pattern matching in model transformations. A constraint contains an expression that must be evaluable into a boolean at the time the transformation rule is applied. When the expression is specified at design time, it is parsed and a syntax tree is generated. If the parsing is not successful, a design time exception occurs. If the parse is successful, the constraint is evaluated every time a match to the pattern is found. No exception will be shown at the time of pattern matching even if the constraint cannot be successfully evaluated. In that case, the constraint will only be considered false. A constraint is satisfied if and only if it can be successfully evaluated and the result is boolean true.
    Since:
    Ptolemy II 7.1
    Version:
    $Id$
    Author:
    Thomas Huining Feng
    Pt.AcceptedRating:
    Red (tfeng)
    Pt.ProposedRating:
    Yellow (tfeng)

    • Method Detail

      • check

        public boolean check​(Pattern pattern,
                     MatchResult matchResult)
        Check whether this constraint is satisfied with the given match in matchResult to the given pattern. A constraint is satisfied if and only if it can be successfully evaluated and the result is boolean true.
        Parameters:
        pattern - The pattern.
        matchResult - The match result.
        Returns:
        true if the constraint is satisfied; false if it cannot be evaluated or the evaluation result is false.

      • _evaluate

        protected void _evaluate​(Pattern pattern,
                         MatchResult matchResult)
                  throws IllegalActionException
        Evaluate the current expression to a token with the given pattern and match result using GTParameter.Evaluator. If this variable was last set directly with a token, then do nothing. In other words, the expression is evaluated only if the value of the token was most recently given by an expression. The expression is also evaluated if any of the variables it refers to have changed since the last evaluation. If the value of this variable changes due to this evaluation, then notify all value dependents and notify the container (if there is one) by calling its attributeChanged() and attributeTypeChanged() methods, as appropriate. An exception is thrown if the expression is illegal, for example if a parse error occurs or if there is a dependency loop.

        If evaluation results in a token that is not of the same type as the current type of the variable, then the type of the variable is changed, unless the new type is incompatible with statically specified types (setTypeEquals() and setTypeAtMost()). If the type is changed, the attributeTypeChanged() method of the container is called. The container can reject the change by throwing an exception.

        This method may trigger a model error, which is delegated up the container hierarchy until an error handler is found, and is ignored if no error handler is found. A model error occurs if the expression cannot be parsed or cannot be evaluated.

        Part of this method is read-synchronized on the workspace.

        Overrides:
        _evaluate in class GTParameter
        Parameters:
        pattern - The pattern.
        matchResult - The match result for the match between the pattern and a host model.
        Throws:
        IllegalActionException - If the expression cannot be parsed or cannot be evaluated, or if a dependency loop is found.