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Description:
A CmpRegion is
a
Region which allows two component Regions (of any class) to be combined to form a more complex
Region. This combination may be performed a boolean AND, OR or XOR (exclusive OR) operator. If
the AND operator is used, then a position is inside the CmpRegion only if it is inside both of its two
component Regions. If the OR operator is used, then a position is inside the CmpRegion if it is inside
either (or both) of its two component Regions. If the XOR operator is used, then a position is inside the
CmpRegion if it is inside one but not both of its two component Regions. Other operators can be
formed by negating one or both component Regions before using them to construct a new
CmpRegion.
The two component Region need not refer to the same coordinate Frame, but it must be possible for
the AST_CONVERT function to determine a Mapping between them (an error will be reported
otherwise when the CmpRegion is created). For instance, a CmpRegion may combine a Region
defined within an ICRS SkyFrame with a Region defined within a Galactic SkyFrame. This is
acceptable because the SkyFrame class knows how to convert between these two systems, and
consequently the AST_CONVERT function will also be able to convert between them. In such cases,
the second component Region will be mapped into the coordinate Frame of the first component
Region, and the Frame represented by the CmpRegion as a whole will be the Frame of the first
component Region.
Since a CmpRegion is itself a Region, it can be used as a component in forming further
CmpRegions. Regions of arbitrary complexity may be built from simple individual Regions in this
way.
Constructor Function
Inheritance
The CmpRegion class
inherits from the Region class.
Attributes
The CmpRegion class does not define any new
attributes beyond those which are applicable to all Regions.
Functions
The CmpRegion
class does not define any new routines beyond those which are applicable to all Regions.
Copyright (C) 2021 East Asian Observatory
- ←Prev
- AST
A Library for Handling
World Coordinate
Systems
in Astronomy - Next→
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