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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.
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 vaues 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
Next: astBegin - Begin a new AST context
Up: AST Function Descriptions
Previous: astAxDistance - Find the distance between two axis values

AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
30th April 2003
E-mail:ussc@star.rl.ac.uk

Copyright (C) 2003 Central Laboratory of the Research Councils