astAxDistance

Find the distance between two axis values

Description:

This function returns a signed value representing the axis increment from axis value v1 to axis value v2.

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

Synopsis

double astAxDistance( AstFrame $\ast$this, int axis, double v1, double v2 )

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 first axis value.
v2
The second axis value.

Returned Value

astAxDistance
The distance from the first to the second 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.