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astAxOffset - Add an increment onto a supplied axis value

Description:
This function returns an axis value formed by adding a signed axis increment onto a supplied axis value.

For a simple Frame, this is a trivial operation returning the sum of the two supplied values. But for other derived classes of Frame (such as a SkyFrame) this is not the case.

Synopsis:
double astAxOffset( AstFrame $*$this, int axis, double v1, double dist )
Parameters:
this
Pointer to the Frame.
axis
The index of the axis to which the supplied values refer. The first axis has index 1.
v1
The original axis value.
dist
The axis increment to add to the original axis value.
Returned Value:
astAxOffset
The incremented axis value.
Notes:
  • This function will return a "bad" result value (AST__BAD) if any of the input values has this value.

  • A "bad" value will also be returned if this function is invoked with the AST error status set, or if it should fail for any reason.


next up previous 264
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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