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Inter-Relating Coordinate Systems (Mappings)

In §4 we used the ZoomMapZoomMap as an example of a MappingMapping. We saw how it could be used to transform coordinates from its input to its output and back again (§4.8). We also saw how its behaviour could be controlled by setting various attributes, such as the ZoomZoom factor and the ReportReport attribute that made it display coordinate values as it transformed them.

In this section, we will look at Mappings a bit more thoroughly and explore the behaviour which is common to all the Mappings provided by AST. This is good background for what follows, because many of the Objects we discuss later will also turn out to be Mappings in various disguises.

Subsections

- The Mapping Class
- The Mapping Model
- Changing Attributes of a Mapping
- Input and Output Coordinate Numbers
- Forward and Inverse Transformations
- Inverting Mappings
- Finding the Rate of Change of a Mapping Output
- Reporting Coordinate Transformations
- Handling Missing (Bad) Coordinate Values
- Example—the UnitMap
- Example—the PermMap