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27 
28 #ifndef INCLUDED_SLIDESHOW_EXPRESSIONNODE_HXX
29 #define INCLUDED_SLIDESHOW_EXPRESSIONNODE_HXX
30 
31 #include "animationfunction.hxx"
32 
33 
34 /* Definition of ExpressionNode interface */
35 
36 namespace slideshow
37 {
38     namespace internal
39     {
40         /** Refinement of AnimationFunction
41 
42 	        This interface is used by the SMIL function parser, to
43 	        collapse constant values into precalculated, single nodes.
44         */
45         class ExpressionNode : public AnimationFunction
46         {
47         public:
48             /** Predicate whether this node is constant.
49 
50         	    This predicate returns true, if this node is
51                 neither time- nor ViewInfo dependent. This allows
52                 for certain obtimizations, i.e. not the full
53                 expression tree needs be represented by
54                 ExpressionNodes.
55 
56                 @returns true, if this node is neither time- nor
57                 ViewInfo dependent
58             */
59             virtual bool isConstant() const = 0;
60         };
61 
62         typedef ::boost::shared_ptr< ExpressionNode > ExpressionNodeSharedPtr;
63     }
64 }
65 
66 #endif /* INCLUDED_SLIDESHOW_EXPRESSIONNODE_HXX */
67