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IntraFlag - IntraMap identification string

Description:
This attribute allows an IntraMap to be flagged so that it is distinguishable from other IntraMaps. The transformation function associated with the IntraMap may then enquire the value of this attribute and adapt the transformation it provides according to the particular IntraMap involved.

Although this is a string attribute, it may often be useful to store numerical values here, encoded as a character string, and to use these as data within the transformation function. Note, however, that this mechanism is not suitable for transferring large amounts of data (more than about 1000 characters) to an IntraMap. For that purpose, global variables are recommended, although the IntraFlag value can be used to supplement this approach. The default IntraFlag value is an empty string.

Type:
String.
Class Applicability:
IntraMap
All IntraMaps have this attribute.
Notes:
  • A pair of IntraMaps whose transformations may potentially cancel cannot be simplified to produce a UnitMap (e.g. using astSimplify) unless they have the same IntraFlag values. The test for equality is case-sensitive.


next up previous 264
Next: Invert - Mapping inversion flag
Up: AST Attribute Descriptions
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AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
24th May 2011
E-mail:ussc@star.rl.ac.uk

Copyright (C) 2009 Science \& Technology Facilities Council