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21 
22 
23 
24 #ifndef INCLUDED_SLIDESHOW_EXPRESSIONNODE_HXX
25 #define INCLUDED_SLIDESHOW_EXPRESSIONNODE_HXX
26 
27 #include "animationfunction.hxx"
28 
29 
30 /* Definition of ExpressionNode interface */
31 
32 namespace slideshow
33 {
34     namespace internal
35     {
36         /** Refinement of AnimationFunction
37 
38 	        This interface is used by the SMIL function parser, to
39 	        collapse constant values into precalculated, single nodes.
40         */
41         class ExpressionNode : public AnimationFunction
42         {
43         public:
44             /** Predicate whether this node is constant.
45 
46         	    This predicate returns true, if this node is
47                 neither time- nor ViewInfo dependent. This allows
48                 for certain obtimizations, i.e. not the full
49                 expression tree needs be represented by
50                 ExpressionNodes.
51 
52                 @returns true, if this node is neither time- nor
53                 ViewInfo dependent
54             */
55             virtual bool isConstant() const = 0;
56         };
57 
58         typedef ::boost::shared_ptr< ExpressionNode > ExpressionNodeSharedPtr;
59     }
60 }
61 
62 #endif /* INCLUDED_SLIDESHOW_EXPRESSIONNODE_HXX */
63