## Changes Introduced in V5.7-2

The following describes the most significant changes which occurred in the AST library between versions V5.7-1 and V5.7-2:

1. The ObjectObject class has a new function astToStringastToString (C only), which creates an in-memory textual serialisation of a given AST Object. A corresponding new function called astFromStringastFromString re-creates the Object from its serialisation.

2. The PolyMapPolyMap class can now use an iterative Newton-Raphson method to evaluate the inverse the inverse transformation if no inverse transformation is defined when the PolyMap is created.

3. The FitsChanFitsChan class has a new method astWriteFitsastWriteFits which writes out all cards currently in the FitsChan to the associated external data sink (specified either by the SinkFileSinkFile attribute or the sink function supplied when the FitsChan was created), and then empties the FitsChan.

4. The FitsChan class has a new read-only attribute called “NkeyNkey”, which holds the number of keywords for which values are held in a FitsChan.

5. The FitsChan astGetFits<X> methods can now be used to returned the value of the current card.

6. The FitsChan class has a new read-only attribute called “CardTypeCardType”, which holds the data type of the keyword value for the current card.

7. The FitsChan class has a new method astReadFitsastReadFits which forces the FitsChan to reads cards from the associated external source and appends them to the end of the FitsChan.

8. - If the FitsChan astReadastRead method reads a FITS header that uses the -SIP (Spitzer) distortion code within the CTYPE values, but which does not provide an inverse polynomial correction, and for which the PolyTran method of the PolyMap class fails to create an accurate estimate of the inverse polynomial correction, then an iterative method will be used to evaluate the inverse correction for each point transformed.