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LSST Data Management Base Package
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Has this mapping been inverted?
If the attribute value is false (the default), the Mapping's behaviour is in the usual direction. However, if it is true then, its two transformations have been inter-changed, so that the Mapping displays the inverse of its native behaviour.
Mapping::inverted returns the inverse of the mapping (e.g. a copy of the mapping with its Invert Invert property set)
All Mappings have this attribute.
The value of the Invert attribute has no effect on the behaviour of a UnitMap.
Inverting a FrameSet will cause its base and current Frames (and its Base Base and FrameSet_Current Current attributes) to be interchanged. This, in turn, may affect other properties and attributes of the FrameSet (such as NIn, NOut, NAxes, TranForward, TranInverse, etc.). The Invert attribute of a FrameSet is not itself affected by selecting a new base or current Frame.
Is the is an instance of a class that always represents a linear transformation?
Note, some Mapping classes can represent linear or non-linear transformations (the MathMap class for instance). Such classes have a false value for the IsLinear attribute. Specific instances of such classes can be tested for linearity using the astLinearApprox function.
All Mappings have this attribute.
The IsLinear value for a CmpMap is determined by the classes of the encapsulated Mappings. For instance, a CmpMap that combines a ZoomMap and a ShiftMap will have a true value for its IsLinear attribute, but a CmpMap that contains a MathMap will have a value of false for its IsLinear attribute.
The @ref Mapping_IsLinear "IsLinear" value for a @ref Frame is `true` (since a @ref Frame is equivalent to a UnitMap).
The @ref Mapping_IsLinear "IsLinear" value for a @ref FrameSet is obtained from the @ref Mapping from the base @ref Frame to the current @ref Frame.
Has the mapping been simplified by the Mapping::simplified method?
If the IsSimple value is true, then the Mapping has been simplified and so there is nothing to be gained by simplifying it again. Indeed, Mapping::simplified will immediately return the Mapping unchanged if IsSimple is true.
All Mappings have this attribute.
All classes of Frame return false for the IsSimple attribute. This is because changes can be made to a Frame which affect the Mapping represented by the Frame, and so there can be no guarantee that the Mapping may not need re-simplifying. Most non-Frame Mappings, on the other hand, are immutable and so when they are simplified it is certain that they will remain in a simple state.
The number of coordinate values for an input point for a Mapping (i.e. the number of dimensions of the space in which the Mapping's input points reside).
All Mappings have this attribute.
If a CmpMap's component Mappings are joined in series then its NIn attribute is equal to the NIn attribute of the first component (or to the NOut attribute of the second component if the the CmpMap is inverted).
If a CmpMap's component Mappings are joined in parallel, then its NIn attribute is given by the sum of the NIn attributes of each component (or the sum of their NOut attributes if the CmpMap is inverted).
The NIn attribute for a Frame is always equal to the number of Frame axes (NAxes attribute).
The NIn attribute of a FrameSet is equal to the number of axes (NAxes attribute) of its base Frame (or the current frame if the FrameSet is inverted). The NIn attribute value may therefore change if a new base Frame or current frame is selected.
The number of coordinate values for an output point for a Mapping (i.e. the number of dimensions of the space in which the Mapping's output points reside).
All Mappings have this attribute.
If a CmpMap's component Mappings are joined in series then its NOut attribute is equal to the NOut attribute of the last component (or to the NIn attribute of the first component if the the CmpMap is inverted).
If a CmpMap's component Mappings are joined in parallel, then its NOut attribute is given by the sum of the NOut attributes of each component (or the sum of their NIn attributes if the CmpMap is inverted).
The NOut attribute for a Frame is always equal to the number of Frame axes (NAxes attribute).
The NOut attribute of a FrameSet is equal to the number of axes (NAxes attribute) of its current Frame (or the base frame if the FrameSet is inverted). The NOut attribute value may therefore change if a new current frame or base frame is selected.
Report transformed coordinates to stdout?
If Report is false (the default), no report is made. However, if it is true, the coordinates of each point are reported (both before and after transformation) by writing them to standard output.
This attribute is provided as an aid to debugging, and to avoid having to report values explicitly in simple programs.
All Mappings have this attribute.
When applied to a compound Mapping (CmpMap), only the Report attribute of the CmpMap, and not those of its component Mappings, is used. Coordinate information is never reported for the component Mappings individually, only for the complete CmpMap.
When applied to any Frame, the formatting capabilities of the Frame (as provided by the Frame::format) will be used to format the reported coordinates.
When applied to any FrameSet, the formatting capabilities of the base and current Frames will be used (as above) to individually format the input and output coordinates, as appropriate. The Report attribute of a FrameSet is not itself affected by selecting a new base or current Frame, but the resulting formatting capabilities may be.
Is the forward transformation defined?
This attribute indicates whether a Mapping is able to transform coordinates in the "forward" direction (i.e. converting input coordinates into output coordinates).
If this attribute is non-zero, the forward transformation is available. Otherwise, it is not.
All Mappings have this attribute.
The TranForward attribute value for a CmpMap is given by the boolean AND of the value for each component Mapping.
The TranForward attribute of a FrameSet applies to the transformation which converts between the FrameSet's base Frame and its current Frame (as specified by the Base and Current attributes).
This value is given by the boolean AND of the TranForward values which apply to each of the individual sub-Mappings required to perform this conversion. The TranForward attribute value for a FrameSet may therefore change if a new base or current Frame is selected.
Is the inverse transformation defined?
This attribute indicates whether a Mapping is able to transform coordinates in the "inverse" direction (i.e. converting input coordinates into output coordinates).
If this attribute is non-zero, the inverse transformation is available. Otherwise, it is not.
All Mappings have this attribute.
The TranInverse attribute value for a CmpMap is given by the boolean AND of the value for each component Mapping.
The TranInverse attribute of a FrameSet applies to the transformation which converts between the FrameSet's current Frame and its base Frame (as specified by the Current and Base attributes).
This value is given by the boolean AND of the TranInverse values which apply to each of the individual sub-Mappings required to perform this conversion. The TranInverse attribute value for a FrameSet may therefore change if a new current or base Frame is selected.
1.9.2