#### Description:

This function adds a new Frame and an associated Mapping to a FrameSet so as to define a new coordinate system, derived from one which already exists within the FrameSet. The new Frame then becomes the FrameSet`’` s current Frame.

This function may also be used to merge two FrameSets, or to append extra axes to every Frame in a FrameSet.

#### Synopsis

void astAddFrame( AstFrameSet ∗this, int iframe, AstMapping ∗map, AstFrame ∗frame )

#### Parameters:

##### this

Pointer to the FrameSet.

##### iframe

The index of the Frame within the FrameSet which describes the coordinate system upon which the new one is to be based. This value should lie in the range from 1 to the number of Frames already in the FrameSet (as given by its Nframe attribute). As a special case, AST__ALLFRAMES may be supplied, in which case the axes defined by the supplied Frame are appended to every Frame in the FrameSet (see the Notes section for details).

##### map

Pointer to a Mapping which describes how to convert coordinates from the old coordinate system (described by the Frame with index `"` iframe`"` ) into coordinates in the new system. The Mapping`’` s forward transformation should perform this conversion, and its inverse transformation should convert in the opposite direction. The supplied Mapping is ignored if parameter `"` iframe`"` is equal to AST__ALLFRAMES.

##### frame

Pointer to a Frame that describes the new coordinate system. Any class of Frame may be supplied (including Regions and FrameSets).

This function may also be used to merge two FrameSets by supplying a pointer to a second FrameSet for this parameter (see the Notes section for details).

#### Notes:

- Deep copies of the supplied `"` mapping`"` and `"` frame`"` objects are stored within the modified FrameSet. So any changes made to the FrameSet after calling this method will have no effect on the supplied Mapping and Frame objects.

- A value of AST__BASE or AST__CURRENT may be given for the `"` iframe`"` parameter to specify the base Frame or the current Frame respectively.

- This function sets the value of the Current attribute for the FrameSet so that the new Frame subsequently becomes the current Frame.

- The number of input coordinate values accepted by the supplied Mapping (its Nin attribute) must match the number of axes in the Frame identified by the `"` iframe`"` parameter. Similarly, the number of output coordinate values generated by this Mapping (its Nout attribute) must match the number of axes in the new Frame.

- As a special case, if a pointer to a FrameSet is given for the `"` frame`"` parameter, this is treated as a request to merge a pair of FrameSets. This is done by appending all the new Frames (in the `"` frame`"` FrameSet) to the original FrameSet, while preserving their order and retaining all the inter-relationships (i.e. Mappings) between them. The two sets of Frames are inter-related within the merged FrameSet by using the Mapping supplied. This should convert between the Frame identified by the `"` iframe`"` parameter (in the original FrameSet) and the current Frame of the `"` frame`"` FrameSet. This latter Frame becomes the current Frame in the merged FrameSet.

- As another special case, if a value of AST__ALLFRAMES is supplied for parameter `"` iframe`"` , then the supplied Mapping is ignored, and the axes defined by the supplied Frame are appended to each Frame in the FrameSet. In detail, each Frame in the FrameSet is replaced by a CmpFrame containing the original Frame and the Frame specified by parameter `"` frame`"` . In addition, each Mapping in the FrameSet is replaced by a CmpMap containing the original Mapping and a UnitMap in parallel. The Nin and Nout attributes of the UnitMap are set equal to the number of axes in the supplied Frame. Each new CmpMap is simplified using astSimplify before being stored in the FrameSet.

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