upgrade ast 8.7.1

1 files changed, 1702 insertions, 0 deletions

diff --git a/ast/xphmap.c b/ast/xphmap.c
new file mode 100644
index 0000000..b8bf030
--- /dev/null
+++ b/ast/xphmap.c
@@ -0,0 +1,1702 @@
+/*
+*class+
+*  Name:
+*     XphMap
+
+*  Purpose:
+*     Transform between different HEALPix projections.
+
+*  Constructor Function:
+*     astXphMap
+
+*  Description:
+*     The XphMap class implements a Mapping between grid coordinates
+*     within different types of HEALPix projection: The available types
+*     are :
+*
+*     - "HPX0":  An HPX projection centred on RA=0h.
+*     - "HPX12": An HPX projection centred on RA=12h.
+*     - "XPHN":  An XPH ("Butterfly") projection centred on the
+*                 north pole.
+*     - "XPHS":  An XPH ("Butterfly") projection centred on the
+*                south pole.
+*
+*     The HPX projection is described in "Mapping on the HEALPix grid"
+*     by Calabretta and Roukema, A&A, 2005. The XPH projection is
+*     described in "Representing the 'butterfly' projection in FITS -
+*     projection code XPH" by Calabretta and Lowe, PASA, 2018.
+*
+*     The forward transformation of an XphMap transforms from grid
+*     coordinates within the nominated projection type into grid
+*     coordinates within an HPX12 projection.
+
+*  Inheritance:
+*     The XphMap class inherits from the Mapping class.
+
+*  Attributes:
+*     The XphMap class does not define any new attributes beyond those
+*     which are applicable to all Mappings.
+
+*  Functions:
+*     The XphMap class does not define any new functions beyond those
+*     which are applicable to all Mappings.
+
+*  Copyright:
+*     Copyright (C) 2018 East Asian Observatory
+
+*  Licence:
+*     This program is free software: you can redistribute it and/or
+*     modify it under the terms of the GNU Lesser General Public
+*     License as published by the Free Software Foundation, either
+*     version 3 of the License, or (at your option) any later
+*     version.
+*
+*     This program is distributed in the hope that it will be useful,
+*     but WITHOUT ANY WARRANTY; without even the implied warranty of
+*     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*     GNU Lesser General Public License for more details.
+*
+*     You should have received a copy of the GNU Lesser General
+*     License along with this program.  If not, see
+*     <http://www.gnu.org/licenses/>.
+
+*  Authors:
+*     DSB: David S. Berry (EAO)
+
+*  History:
+*     18-OCT-2018 (DSB):
+*        Original version.
+*class-
+*/
+
+/* Module Macros. */
+/* ============== */
+/* Set the name of the class we are implementing. This indicates to
+   the header files that define class interfaces that they should make
+   "protected" symbols available. */
+#define astCLASS XphMap
+
+/* Include files. */
+/* ============== */
+/* Interface definitions. */
+/* ---------------------- */
+
+#include "globals.h"             /* Thread-safe global data access */
+#include "error.h"               /* Error reporting facilities */
+#include "memory.h"              /* Memory allocation facilities */
+#include "globals.h"             /* Thread-safe global data access */
+#include "object.h"              /* Base Object class */
+#include "pointset.h"            /* Sets of points/coordinates */
+#include "mapping.h"             /* Coordinate mappings (parent class) */
+#include "channel.h"             /* I/O channels */
+#include "unitmap.h"             /* Unit Mappings */
+#include "matrixmap.h"           /* Matrix Mappings */
+#include "xphmap.h"              /* Interface definition for this class */
+
+/* Error code definitions. */
+/* ----------------------- */
+#include "ast_err.h"             /* AST error codes */
+
+/* C header files. */
+/* --------------- */
+#include <float.h>
+#include <math.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+
+/* Module Variables. */
+/* ================= */
+
+/* Names and descriptions of each type of XphMap. These should correspond
+   to the values of constants AST__HPX0, AST__HPX12, AST__XPHN and AST__XPHS
+   in xphmap.h */
+static const char *proj_name[] = { "HPX0", "HPX12", "XPHN", "XPHS" };
+static const char *proj_comm[] = { "HPX projection centred on RA=0h",
+                                   "HPX projection centred on RA=12h",
+                                   "XPH projection centred on north pole",
+                                   "XPH projection centred on south pole" };
+
+/* Address of this static variable is used as a unique identifier for
+   member of this class. */
+static int class_check;
+
+/* Pointers to parent class methods which are extended by this class. */
+static AstPointSet *(* parent_transform)( AstMapping *, AstPointSet *, int, AstPointSet *, int * );
+
+/* Define macros for accessing each item of thread specific global data. */
+#ifdef THREAD_SAFE
+
+/* Define how to initialise thread-specific globals. */
+#define GLOBAL_inits \
+   globals->Class_Init = 0;
+
+/* Create the function that initialises global data for this module. */
+astMAKE_INITGLOBALS(XphMap)
+
+/* Define macros for accessing each item of thread specific global data. */
+#define class_init astGLOBAL(XphMap,Class_Init)
+#define class_vtab astGLOBAL(XphMap,Class_Vtab)
+#define getattrib_buff astGLOBAL(XphMap,GetAttrib_Buff)
+
+
+
+/* If thread safety is not needed, declare and initialise globals at static
+   variables. */
+#else
+
+/* Define the class virtual function table and its initialisation flag
+   as static variables. */
+static AstXphMapVtab class_vtab;   /* Virtual function table */
+static int class_init = 0;         /* Virtual function table initialised? */
+
+#endif
+
+/* External Interface Function Prototypes. */
+/* ======================================= */
+/* The following functions have public prototypes only (i.e. no
+   protected prototypes), so we must provide local prototypes for use
+   within this module. */
+AstXphMap *astXphMapId_( int, int, const char *, ... );
+
+/* Prototypes for Private Member Functions. */
+/* ======================================== */
+static AstPointSet *Transform( AstMapping *, AstPointSet *, int, AstPointSet *, int * );
+static int Equal( AstObject *, AstObject *, int * );
+static int GetIsLinear( AstMapping *, int * );
+static int MapMerge( AstMapping *, int, int, int *, AstMapping ***, int **, int * );
+static void Dump( AstObject *, AstChannel *, int * );
+
+/* Member functions. */
+/* ================= */
+
+static int Equal( AstObject *this_object, AstObject *that_object, int *status ) {
+/*
+*  Name:
+*     Equal
+
+*  Purpose:
+*     Test if two XphMaps are equivalent.
+
+*  Type:
+*     Private function.
+
+*  Synopsis:
+*     #include "xphmap.h"
+*     int Equal( AstObject *this, AstObject *that, int *status )
+
+*  Class Membership:
+*     XphMap member function (over-rides the astEqual protected
+*     method inherited from the astMapping class).
+
+*  Description:
+*     This function returns a boolean result (0 or 1) to indicate whether
+*     two XphMaps are equivalent.
+
+*  Parameters:
+*     this
+*        Pointer to the first Object (a XphMap).
+*     that
+*        Pointer to the second Object.
+*     status
+*        Pointer to the inherited status variable.
+
+*  Returned Value:
+*     One if the XphMaps are equivalent, zero otherwise.
+
+*  Notes:
+*     - A value of zero will be returned if this function is invoked
+*     with the global status set, or if it should fail for any reason.
+*/
+
+/* Local Variables: */
+   AstXphMap *that;
+   AstXphMap *this;
+   int result;
+
+/* Initialise. */
+   result = 0;
+
+/* Check the global error status. */
+   if ( !astOK ) return result;
+
+/* Obtain pointers to the two XphMap structures. */
+   this = (AstXphMap *) this_object;
+   that = (AstXphMap *) that_object;
+
+/* Check the second object is a XphMap. We know the first is a
+   XphMap since we have arrived at this implementation of the virtual
+   function. */
+   if( astIsAXphMap( that ) ) {
+
+/* Check the properties of the two XphMaps are equal. */
+      if( astGetInvert( this ) == astGetInvert( that ) ) {
+         result = ( this->type == that->type ) &&
+                  ( this->order == that->order );
+      }
+   }
+
+/* Return the result, */
+   return result;
+}
+
+static int GetIsLinear( AstMapping *this_mapping, int *status ){
+/*
+*  Name:
+*     GetIsLinear
+
+*  Purpose:
+*     Return the value of the IsLinear attribute for a XphMap.
+
+*  Type:
+*     Private function.
+
+*  Synopsis:
+*     #include "mapping.h"
+*     void GetIsLinear( AstMapping *this, int *status )
+
+*  Class Membership:
+*     XphMap member function (over-rides the protected astGetIsLinear
+*     method inherited from the Mapping class).
+
+*  Description:
+*     This function returns the value of the IsLinear attribute for a
+*     Frame, which is always one.
+
+*  Parameters:
+*     this
+*        Pointer to the XphMap.
+*     status
+*        Pointer to the inherited status variable.
+*/
+   return (((AstXphMap *) this_mapping)->type == AST__HPX12 );
+}
+
+void astInitXphMapVtab_(  AstXphMapVtab *vtab, const char *name, int *status ) {
+/*
+*+
+*  Name:
+*     astInitXphMapVtab
+
+*  Purpose:
+*     Initialise a virtual function table for a XphMap.
+
+*  Type:
+*     Protected function.
+
+*  Synopsis:
+*     #include "xphmap.h"
+*     void astInitXphMapVtab( AstXphMapVtab *vtab, const char *name )
+
+*  Class Membership:
+*     XphMap vtab initialiser.
+
+*  Description:
+*     This function initialises the component of a virtual function
+*     table which is used by the XphMap class.
+
+*  Parameters:
+*     vtab
+*        Pointer to the virtual function table. The components used by
+*        all ancestral classes will be initialised if they have not already
+*        been initialised.
+*     name
+*        Pointer to a constant null-terminated character string which contains
+*        the name of the class to which the virtual function table belongs (it
+*        is this pointer value that will subsequently be returned by the Object
+*        astClass function).
+*-
+*/
+
+/* Local Variables: */
+   astDECLARE_GLOBALS            /* Pointer to thread-specific global data */
+   AstObjectVtab *object;        /* Pointer to Object component of Vtab */
+   AstMappingVtab *mapping;      /* Pointer to Mapping component of Vtab */
+
+/* Check the local error status. */
+   if ( !astOK ) return;
+
+/* Get a pointer to the thread specific global data structure. */
+   astGET_GLOBALS(NULL);
+
+/* Initialize the component of the virtual function table used by the
+   parent class. */
+   astInitMappingVtab( (AstMappingVtab *) vtab, name );
+
+/* Store a unique "magic" value in the virtual function table. This
+   will be used (by astIsAXphMap) to determine if an object belongs
+   to this class.  We can conveniently use the address of the (static)
+   class_check variable to generate this unique value. */
+   vtab->id.check = &class_check;
+   vtab->id.parent = &(((AstMappingVtab *) vtab)->id);
+
+/* Initialise member function pointers. */
+/* ------------------------------------ */
+/* Store pointers to the member functions (implemented here) that provide
+   virtual methods for this class. */
+
+/* Save the inherited pointers to methods that will be extended, and
+   replace them with pointers to the new member functions. */
+   object = (AstObjectVtab *) vtab;
+   mapping = (AstMappingVtab *) vtab;
+
+   parent_transform = mapping->Transform;
+   mapping->Transform = Transform;
+
+/* Store replacement pointers for methods which will be over-ridden by
+   new member functions implemented here. */
+   object->Equal = Equal;
+   mapping->MapMerge = MapMerge;
+   mapping->GetIsLinear = GetIsLinear;
+
+/* Declare the class dump function. There is no copy constructor or
+   destructor. */
+   astSetDump( vtab, Dump, "XphMap", "HPX variant mapping" );
+
+/* If we have just initialised the vtab for the current class, indicate
+   that the vtab is now initialised, and store a pointer to the class
+   identifier in the base "object" level of the vtab. */
+   if( vtab == &class_vtab ) {
+      class_init = 1;
+      astSetVtabClassIdentifier( vtab, &(vtab->id) );
+   }
+}
+
+static int MapMerge( AstMapping *this, int where, int series, int *nmap,
+                     AstMapping ***map_list, int **invert_list, int *status ) {
+/*
+*  Name:
+*     MapMerge
+
+*  Purpose:
+*     Simplify a sequence of Mappings containing a XphMap.
+
+*  Type:
+*     Private function.
+
+*  Synopsis:
+*     #include "mapping.h"
+*     int MapMerge( AstMapping *this, int where, int series, int *nmap,
+*                   AstMapping ***map_list, int **invert_list, int *status )
+
+*  Class Membership:
+*     XphMap method (over-rides the protected astMapMerge method
+*     inherited from the Mapping class).
+
+*  Description:
+*     This function attempts to simplify a sequence of Mappings by
+*     merging a nominated XphMap in the sequence with its neighbours,
+*     so as to shorten the sequence if possible.
+*
+*     In many cases, simplification will not be possible and the
+*     function will return -1 to indicate this, without further
+*     action.
+*
+*     In most cases of interest, however, this function will either
+*     attempt to replace the nominated XphMap with one which it
+*     considers simpler, or to merge it with the Mappings which
+*     immediately precede it or follow it in the sequence (both will
+*     normally be considered). This is sufficient to ensure the
+*     eventual simplification of most Mapping sequences by repeated
+*     application of this function.
+*
+*     In some cases, the function may attempt more elaborate
+*     simplification, involving any number of other Mappings in the
+*     sequence. It is not restricted in the type or scope of
+*     simplification it may perform, but will normally only attempt
+*     elaborate simplification in cases where a more straightforward
+*     approach is not adequate.
+
+*  Parameters:
+*     this
+*        Pointer to the nominated XphMap which is to be merged with
+*        its neighbours. This should be a cloned copy of the XphMap
+*        pointer contained in the array element "(*map_list)[where]"
+*        (see below). This pointer will not be annulled, and the
+*        XphMap it identifies will not be modified by this function.
+*     where
+*        Index in the "*map_list" array (below) at which the pointer
+*        to the nominated XphMap resides.
+*     series
+*        A non-zero value indicates that the sequence of Mappings to
+*        be simplified will be applied in series (i.e. one after the
+*        other), whereas a zero value indicates that they will be
+*        applied in parallel (i.e. on successive sub-sets of the
+*        input/output coordinates).
+*     nmap
+*        Address of an int which counts the number of Mappings in the
+*        sequence. On entry this should be set to the initial number
+*        of Mappings. On exit it will be updated to record the number
+*        of Mappings remaining after simplification.
+*     map_list
+*        Address of a pointer to a dynamically allocated array of
+*        Mapping pointers (produced, for example, by the astMapList
+*        method) which identifies the sequence of Mappings. On entry,
+*        the initial sequence of Mappings to be simplified should be
+*        supplied.
+*
+*        On exit, the contents of this array will be modified to
+*        reflect any simplification carried out. Any form of
+*        simplification may be performed. This may involve any of: (a)
+*        removing Mappings by annulling any of the pointers supplied,
+*        (b) replacing them with pointers to new Mappings, (c)
+*        inserting additional Mappings and (d) changing their order.
+*
+*        The intention is to reduce the number of Mappings in the
+*        sequence, if possible, and any reduction will be reflected in
+*        the value of "*nmap" returned. However, simplifications which
+*        do not reduce the length of the sequence (but improve its
+*        execution time, for example) may also be performed, and the
+*        sequence might conceivably increase in length (but normally
+*        only in order to split up a Mapping into pieces that can be
+*        more easily merged with their neighbours on subsequent
+*        invocations of this function).
+*
+*        If Mappings are removed from the sequence, any gaps that
+*        remain will be closed up, by moving subsequent Mapping
+*        pointers along in the array, so that vacated elements occur
+*        at the end. If the sequence increases in length, the array
+*        will be extended (and its pointer updated) if necessary to
+*        accommodate any new elements.
+*
+*        Note that any (or all) of the Mapping pointers supplied in
+*        this array may be annulled by this function, but the Mappings
+*        to which they refer are not modified in any way (although
+*        they may, of course, be deleted if the annulled pointer is
+*        the final one).
+*     invert_list
+*        Address of a pointer to a dynamically allocated array which,
+*        on entry, should contain values to be assigned to the Invert
+*        attributes of the Mappings identified in the "*map_list"
+*        array before they are applied (this array might have been
+*        produced, for example, by the astMapList method). These
+*        values will be used by this function instead of the actual
+*        Invert attributes of the Mappings supplied, which are
+*        ignored.
+*
+*        On exit, the contents of this array will be updated to
+*        correspond with the possibly modified contents of the
+*        "*map_list" array.  If the Mapping sequence increases in
+*        length, the "*invert_list" array will be extended (and its
+*        pointer updated) if necessary to accommodate any new
+*        elements.
+*     status
+*        Pointer to the inherited status variable.
+
+*  Returned Value:
+*     If simplification was possible, the function returns the index
+*     in the "map_list" array of the first element which was
+*     modified. Otherwise, it returns -1 (and makes no changes to the
+*     arrays supplied).
+
+*  Notes:
+*     - A value of -1 will be returned if this function is invoked
+*     with the global error status set, or if it should fail for any
+*     reason.
+*/
+
+/* Local Variables: */
+   AstMapping *new;              /* Pointer to replacement Mapping */
+   const char *class;            /* Pointer to Mapping class string */
+   int cancel;                   /* Do mappings cancel? */
+   int imap1;                    /* Index of first XphMap */
+   int imap2;                    /* Index of last XphMap */
+   int imap;                     /* Loop counter for Mappings */
+   int old_invert1;              /* Original Invert flag for map1 */
+   int old_invert2;              /* Original Invert flag for map2 */
+   int result;                   /* Result value to return */
+
+/* Initialise the returned result. */
+   result = -1;
+
+/* Check the global error status. */
+   if ( !astOK ) return result;
+
+/* Note, an XphMap with a type of AST__HPX12 is not equivalent to a UnitMap
+   because it performs clipping of out-of-bounds input positions, even
+   though input positions that are within bounds are copied unchanged. */
+
+/* In series. */
+/* ---------- */
+/* Handle the case where the Mappings are connected in series. */
+   if ( series ) {
+
+/* Look for an adjacent XphMap. */
+      imap1 = -1;
+      imap2 = -1;
+
+      if( where > 0 ) {
+         class = astGetClass( ( *map_list )[ where - 1 ] );
+         if ( astOK && !strcmp( class, "XphMap" ) ) {
+            imap1 = where - 1;
+            imap2 = where;
+         }
+      }
+
+      if( imap1 == -1 && where < *nmap - 1 ) {
+         class = astGetClass( ( *map_list )[ where + 1 ] );
+         if ( astOK && !strcmp( class, "XphMap" ) ) {
+            imap1 = where;
+            imap2 = where + 1;
+         }
+      }
+
+/* If one was found, check to see if the two adjacent XphMaps cancel out. */
+      if( imap1 != -1 ) {
+
+/* Ensure they have the required Invert flags, saving the original
+   values first so they can be re-instated later. */
+         old_invert1 = astGetInvert( ( *map_list )[ imap1 ] );
+         old_invert2 = astGetInvert( ( *map_list )[ imap2 ] );
+         astSetInvert( ( *map_list )[ imap1 ], ( *invert_list )[ imap1 ] );
+         astSetInvert( ( *map_list )[ imap2 ], ( *invert_list )[ imap2 ] );
+
+/* They cancel out if they are equal and opposite. So invert one and then
+   compare them for equality. */
+         astInvert( ( *map_list )[ imap1 ] );
+         cancel = astEqual( ( *map_list )[ imap1 ], ( *map_list )[ imap2 ] );
+         astInvert( ( *map_list )[ imap1 ] );
+
+/* Reinstate the original Invert flags. */
+         astSetInvert( ( *map_list )[ imap1 ], old_invert1 );
+         astSetInvert( ( *map_list )[ imap2 ], old_invert2 );
+
+/* Replace the two XphMaps with a UnitMap if they cancel. */
+         if( cancel ) {
+
+/* Annul the old Mapping pointers */
+            ( *map_list )[ imap1 ] = astAnnul( ( *map_list )[ imap1 ] );
+            ( *map_list )[ imap2 ] = astAnnul( ( *map_list )[ imap2 ] );
+
+/* Create the UnitMap. */
+            new = (AstMapping *) astUnitMap( 2, "", status );
+
+/* Insert the pointer to the replacement Mapping and initialise its
+   invert flag. */
+            ( *map_list )[ imap1 ] = new;
+            ( *invert_list )[ imap1 ] = 0;
+
+/* Loop to close the resulting gap by moving subsequent elements down
+   in the arrays. */
+            for ( imap = imap2 + 1; imap < *nmap; imap++ ) {
+               ( *map_list )[ imap - 1 ] = ( *map_list )[ imap ];
+               ( *invert_list )[ imap - 1 ] = ( *invert_list )[ imap ];
+            }
+
+/* Clear the vacated elements at the end. */
+            ( *map_list )[ *nmap - 1 ] = NULL;
+            ( *invert_list )[ *nmap - 1 ] = 0;
+
+/* Decrement the Mapping count and return the index of the first
+   modified element. */
+            ( *nmap )--;
+            result = imap1;
+         }
+      }
+   }
+
+/* If an error occurred, clear the returned result. */
+   if ( !astOK ) result = -1;
+
+/* Return the result. */
+   return result;
+}
+
+static AstPointSet *Transform( AstMapping *this, AstPointSet *in,
+                               int forward, AstPointSet *out, int *status ) {
+/*
+*  Name:
+*     Transform
+
+*  Purpose:
+*     Apply a XphMap to transform a set of points.
+
+*  Type:
+*     Private function.
+
+*  Synopsis:
+*     #include "xphmap.h"
+*     AstPointSet *Transform( AstMapping *this, AstPointSet *in,
+*                             int forward, AstPointSet *out, int *status )
+
+*  Class Membership:
+*     XphMap member function (over-rides the astTransform protected
+*     method inherited from the Mapping class).
+
+*  Description:
+*     This function takes a XphMap and a set of points encapsulated in a
+*     PointSet and transforms the points so as to apply the required zoom
+*     factor.
+
+*  Parameters:
+*     this
+*        Pointer to the XphMap.
+*     in
+*        Pointer to the PointSet holding the input coordinate data.
+*     forward
+*        A non-zero value indicates that the forward coordinate transformation
+*        should be applied, while a zero value requests the inverse
+*        transformation.
+*     out
+*        Pointer to a PointSet which will hold the transformed (output)
+*        coordinate values. A NULL value may also be given, in which case a
+*        new PointSet will be created by this function.
+*     status
+*        Pointer to the inherited status variable.
+
+*  Returned Value:
+*     Pointer to the output (possibly new) PointSet.
+
+*  Notes:
+*     -  A null pointer will be returned if this function is invoked with the
+*     global error status set, or if it should fail for any reason.
+*     -  The number of coordinate values per point in the input PointSet must
+*     match the number of coordinates for the XphMap being applied.
+*     -  If an output PointSet is supplied, it must have space for sufficient
+*     number of points and coordinate values per point to accommodate the
+*     result. Any excess space will be ignored.
+*/
+
+/* Local Variables: */
+   AstPointSet *result;          /* Pointer to output PointSet */
+   AstXphMap *map;               /* Pointer to XphMap to be applied */
+   double **ptr_in;              /* Pointer to input coordinate data */
+   double **ptr_out;             /* Pointer to output coordinate data */
+   double *px_in;                /* Pointer to next input X value */
+   double *px_out;               /* Pointer to next output X value */
+   double *py_in;                /* Pointer to next input Y value */
+   double *py_out;               /* Pointer to next output Y value */
+   int d;                        /* Difference between x and y grid indices */
+   int fx;                       /* Facet offset along X axis */
+   int fy;                       /* Facet offset along Y axis */
+   int ix;                       /* Nearest integer to X value */
+   int iy;                       /* Nearest integer to Y value */
+   int n2;                       /* Two times nppf */
+   int n3;                       /* Three times nppf */
+   int n4;                       /* Four times nppf */
+   int n5;                       /* Five times nppf */
+   int n6;                       /* Six times nppf */
+   int n7;                       /* Seven times nppf */
+   int n9;                       /* Nine times nppf */
+   int npoint;                   /* Number of points */
+   int nppf;                     /* No. of pixels per facet */
+   int point;                    /* Loop counter for points */
+   int s;                        /* Sum of x and y grid indices */
+
+/* Check the global error status. */
+   if ( !astOK ) return NULL;
+
+/* Obtain a pointer to the XphMap. */
+   map = (AstXphMap *) this;
+
+/* Apply the parent mapping using the stored pointer to the Transform member
+   function inherited from the parent Mapping class. This function validates
+   all arguments and generates an output PointSet if necessary, but does not
+   actually transform any coordinate values. */
+   result = (*parent_transform)( this, in, forward, out, status );
+
+/* We will now extend the parent astTransform method by performing the
+   calculations needed to generate the output coordinate values. */
+
+/* Determine the numbers of points and coordinates per point from the input
+   PointSet and obtain pointers for accessing the input and output coordinate
+   values. */
+   npoint = astGetNpoint( in );
+   ptr_in = astGetPoints( in );
+   ptr_out = astGetPoints( result );
+
+/* Determine whether to apply the forward or inverse mapping, according to the
+   direction specified and whether the mapping has been inverted. */
+   if ( astGetInvert( map ) ) forward = !forward;
+
+/* Get the number of pixels per facet. */
+   nppf = ( 1 << map->order );
+   n2 = 2*nppf;
+   n3 = 3*nppf;
+   n4 = 4*nppf;
+   n5 = 5*nppf;
+   n6 = 6*nppf;
+   n7 = 7*nppf;
+   n9 = 9*nppf;
+
+/* Perform coordinate arithmetic. */
+/* ------------------------------ */
+   if ( astOK ) {
+      px_in = ptr_in[ 0 ];
+      py_in = ptr_in[ 1 ];
+      px_out = ptr_out[ 0 ];
+      py_out = ptr_out[ 1 ];
+
+/* Forward transformation - from "type" to HPX12. */
+      if( forward ) {
+
+/* Transforming from HPX12 to HPX12 is a unit transformation, except that
+   we need to check for out-of-bounds input positions, which are set bad
+   in the output. */
+         if( map->type == AST__HPX12 ){
+            for ( point = 0; point < npoint; point++,
+                  px_in++,py_in++,px_out++,py_out++ ) {
+
+/* Check the input values are good */
+               if ( *px_in == AST__BAD || *py_in == AST__BAD ) {
+                  *px_out = AST__BAD;
+                  *py_out = AST__BAD;
+
+/* Get the zero-based integer indices of the grid cell containing the
+   input position. The cell boundaries on the low RA edges are considered
+   to be in the cell. Those on the high RA edges are considered to be part
+   of the neigbouring cell. */
+               } else {
+                  ix = ceil( *px_in - 1.5 );
+                  iy = ceil( *py_in - 1.5 );
+
+/* Get the zero-based facet (x,y) indices - offsets from the bottom left
+   facet. */
+                  fx = ix/nppf;
+                  fy = iy/nppf;
+
+/* Check that the facet indices are legal. */
+                  if( fx >= 0 && fx < 5 && fy >= 0 && fy < 5 &&
+                      abs( fx - fy ) <= 1 ) {
+
+/* Get the sum of the zero-based x and y grid indices, plus one. */
+                     s = ix + iy + 1;
+
+/* The bottom left half of the bottom left facet and the top right half
+   of the top right facet are illegal. */
+                     if( s <= nppf || s > n9 ) {
+                        *px_out = AST__BAD;
+                        *py_out = AST__BAD;
+
+/* Other positions are copied unchanged. */
+                     } else {
+                        *px_out = *px_in;
+                        *py_out = *py_in;
+                     }
+
+                  } else {
+                     *px_out = AST__BAD;
+                     *py_out = AST__BAD;
+                  }
+               }
+            }
+
+/* Transforming from HPX0 to HPX12 - swap the top right and bottom left
+   halves of the whole sky map. */
+         } else if( map->type == AST__HPX0 ){
+            for ( point = 0; point < npoint; point++,
+                  px_in++,py_in++,px_out++,py_out++ ) {
+
+/* Check for bad input coordinates */
+               if ( *px_in == AST__BAD || *py_in == AST__BAD ) {
+                  *px_out = AST__BAD;
+                  *py_out = AST__BAD;
+               } else {
+
+/* Get the zero-based integer indices of the grid cell containing the
+   input position. The cell boundaries on the low RA edges are considered
+   to be in the cell. Those on the high RA edges are considered to be part
+   of the neigbouring cell. */
+                  ix = ceil( *px_in - 1.5 );
+                  iy = ceil( *py_in - 1.5 );
+
+/* Get the facet indices and check they are legal. */
+                  fx = ix/nppf;
+                  fy = iy/nppf;
+                  if( fx >= 0 && fx < 5 && fy >= 0 && fy < 5 &&
+                      abs( fx - fy ) <= 1 ) {
+
+/* Get the sum of the zero-based x and y grid indices, plus one. */
+                     s = ix + iy + 1;
+
+/* The bottom left half of the bottom left facet and the top right half
+   of the top right facet are illegal. */
+                     if( s <= nppf || s > n9 ) {
+                        *px_out = AST__BAD;
+                        *py_out = AST__BAD;
+
+/* Other input positions in the bottom left half of the whole-sky map get
+   moved to the top right by adding 2*nppf on each axis. */
+                     } else if( s <= n5 ) {
+                        *px_out = *px_in + n2;
+                        *py_out = *py_in + n2;
+
+/* Other input positions in the rop right half of the whole-sky map get
+   moved to the bottom left by subtracting 2*nppf on each axis. */
+                     } else {
+                        *px_out = *px_in - n2;
+                        *py_out = *py_in - n2;
+                     }
+
+                  } else {
+                     *px_out = AST__BAD;
+                     *py_out = AST__BAD;
+                  }
+               }
+            }
+
+/* Transforming from XPHN to HPX12 */
+         } else if( map->type == AST__XPHN ){
+            for ( point = 0; point < npoint; point++,
+                  px_in++,py_in++,px_out++,py_out++ ) {
+
+/* Check for bad input coordinates */
+               if ( *px_in == AST__BAD || *py_in == AST__BAD ) {
+                  *px_out = AST__BAD;
+                  *py_out = AST__BAD;
+               } else {
+
+/* The transformation depends on the gore containing the supplied position.
+   A gore contains its low RA boundaries, but not its high RA boundaries.
+   First do gore 0. */
+                  if( *px_in < n2 + 0.5 && *py_in >= n2 + 0.5 ) {
+
+/* Get the zero-based integer indices of the grid cell containing the
+   input position. The cell boundaries on the low RA edges are considered
+   to be in the cell. Those on the high RA edges are considered to be part
+   of the neigbouring cell. */
+                     ix = floor( *px_in - 0.5 );
+                     iy = floor( *py_in - 0.5 );
+
+/* Check that the cell containing the input position is contained with
+   the used part of the gore, and if so, do the appropriate transformation. */
+                     s = ix + iy + 1;
+                     if( s < n5 && s >= n3 ) {
+                        *px_out = n4 + 1.0 - *px_in;
+                        *py_out = n6 + 1.0 - *py_in;
+                     } else {
+                        *px_out = AST__BAD;
+                        *py_out = AST__BAD;
+                     }
+
+/* Do the same for input positions within gore 3. */
+                  } else if( *px_in >= n2 + 0.5 && *py_in > n2 + 0.5 ) {
+                     ix = floor( *px_in - 0.5 );
+                     iy = ceil( *py_in - 1.5 );
+
+                     d = ix - iy;
+                     if( d >= -nppf && d < nppf ) {
+                        *px_out = *py_in - nppf;
+                        *py_out = n5 + 1.0 - *px_in;
+                     } else {
+                        *px_out = AST__BAD;
+                        *py_out = AST__BAD;
+                     }
+
+/* Do the same for input positions within gore 2. */
+                  } else if( *px_in > n2 + 0.5 && *py_in <= n2 + 0.5 ) {
+                     ix = ceil( *px_in - 1.5 );
+                     iy = ceil( *py_in - 1.5 );
+
+                     s = ix + iy + 1;
+                     if( s > n3 && s <= n5 ) {
+                        *px_out = *px_in - n2;
+                        *py_out = *py_in;
+                     } else {
+                        *px_out = AST__BAD;
+                        *py_out = AST__BAD;
+                     }
+
+/* Do the same for input positions within gore 1. */
+                  } else {
+                     ix = ceil( *px_in - 1.5 );
+                     iy = floor( *py_in - 0.5 );
+
+                     d = ix - iy;
+                     if( d > -nppf && d <= nppf ) {
+                        *px_out = n5 + 1.0 - *py_in;
+                        *py_out = n3 + *px_in;
+                     } else {
+                        *px_out = AST__BAD;
+                        *py_out = AST__BAD;
+                     }
+                  }
+               }
+            }
+
+/* Transforming from XPHS to HPX12 */
+         } else if( map->type == AST__XPHS ){
+            for ( point = 0; point < npoint; point++,
+                  px_in++,py_in++,px_out++,py_out++ ) {
+
+/* Check for bad input coordinates */
+               if ( *px_in == AST__BAD || *py_in == AST__BAD ) {
+                  *px_out = AST__BAD;
+                  *py_out = AST__BAD;
+               } else {
+
+/* The transformation depends on the gore containing the supplied position.
+   A gore contains its low RA boundaries, but not its high RA boundaries.
+   First do gore 0. */
+                  if( *px_in < n2 + 0.5 && *py_in <= n2 + 0.5 ) {
+
+/* Get the zero-based integer indices of the grid cell containing the
+   input position. The cell boundaries on the low RA edges are considered
+   to be in the cell. Those on the high RA edges are considered to be part
+   of the neigbouring cell. */
+                     ix = floor( *px_in - 0.5 );
+                     iy = ceil( *py_in - 1.5 );
+
+/* Check that the cell containing the input position is contained with
+   the used part of the gore, and if so, do the appropriate transformation. */
+                     d = ix - iy;
+                     if( d >= -nppf && d < nppf ) {
+                        *px_out = n2 + *py_in;
+                        *py_out = n4 + 1.0 - *px_in;
+                     } else {
+                        *px_out = AST__BAD;
+                        *py_out = AST__BAD;
+                     }
+
+/* Do the same for input positions within gore 3. */
+                  } else if( *px_in >= n2 + 0.5 && *py_in < n2 + 0.5 ) {
+                     ix = floor( *px_in - 0.5 );
+                     iy = floor( *py_in - 0.5 );
+
+                     s = ix + iy + 1;
+                     if( s >= n3 && s < n5 ) {
+                        *px_out = n5 + 1.0 - *px_in;
+                        *py_out = n3 + 1.0 - *py_in;
+                     } else {
+                        *px_out = AST__BAD;
+                        *py_out = AST__BAD;
+                     }
+
+/* Do the same for input positions within gore 2. */
+                  } else if( *px_in > n2 + 0.5 && *py_in >= n2 + 0.5 ) {
+                     ix = ceil( *px_in - 1.5 );
+                     iy = floor( *py_in - 0.5 );
+
+                     d = ix - iy;
+                     if( d <= nppf && d > -nppf ) {
+                        *px_out = n4 + 1 - *py_in;
+                        *py_out = *px_in - n2;
+                     } else {
+                        *px_out = AST__BAD;
+                        *py_out = AST__BAD;
+                     }
+
+/* Do the same for input positions within gore 1. */
+                  } else {
+                     ix = ceil( *px_in - 1.5 );
+                     iy = ceil( *py_in - 1.5 );
+
+                     s = ix + iy + 1;
+                     if( s <= n5 && s > n3 ) {
+                        *px_out = n3 + *px_in;
+                        *py_out = nppf + *py_in;
+                     } else {
+                        *px_out = AST__BAD;
+                        *py_out = AST__BAD;
+                     }
+                  }
+               }
+            }
+
+/* Unknown projection code */
+         } else if( astOK ) {
+            astError( AST__INTER, "astTransform(%s): Invalid projection type "
+                      "encountered (%d) (internal programming error).", status,
+                      astGetClass(this), map->type );
+         }
+
+/* Inverse transformation - from HPX12 to "type". */
+      } else {
+
+/* Transforming from HPX12 to HPX12 is a unit transformation, except that
+   we need to check that input positions within a split input facet are
+   moved to the equivalent normalised output positions. */
+         if( map->type == AST__HPX12 ){
+            for ( point = 0; point < npoint; point++,
+                  px_in++,py_in++,px_out++,py_out++ ) {
+
+/* Check the input values are good */
+               if ( *px_in == AST__BAD || *py_in == AST__BAD ) {
+                  *px_out = AST__BAD;
+                  *py_out = AST__BAD;
+
+/* Get the zero-based integer indices of the grid cell containing the
+   input position. The cell boundaries on the low RA edges are considered
+   to be in the cell. Those on the high RA edges are considered to be part
+   of the neigbouring cell. */
+               } else {
+                  ix = ceil( *px_in - 1.5 );
+                  iy = ceil( *py_in - 1.5 );
+
+/* Get the zero-based facet (x,y) indices - offsets from the bottom left
+   facet in Calabretta & Roukema 2005 Fig 3. */
+                  fx = ix/nppf;
+                  fy = iy/nppf;
+
+/* Check that the facet indices are legal. */
+                  if( fx >= 0 && fx < 5 && fy >= 0 && fy < 5 &&
+                      abs( fx - fy ) <= 1 ) {
+
+/* Get the sum of the zero-based x and y grid indices, plus one. */
+                     s = ix + iy + 1;
+
+/* The bottom left half of the bottom left facet and the top right half
+   of the top right facet are illegal. */
+                     if( s <= nppf || s > n9 ) {
+                        *px_out = AST__BAD;
+                        *py_out = AST__BAD;
+
+/* Other positions are copied unchanged. */
+                     } else {
+                        *px_out = *px_in;
+                        *py_out = *py_in;
+                     }
+
+                  } else {
+                     *px_out = AST__BAD;
+                     *py_out = AST__BAD;
+                  }
+               }
+            }
+
+/* Transforming from HPX12 to HPX0 - swap the top right and bottom left
+   halves of the whole sky map. */
+         } else if( map->type == AST__HPX0 ){
+            for ( point = 0; point < npoint; point++,
+                  px_in++,py_in++,px_out++,py_out++ ) {
+
+               if ( *px_in == AST__BAD || *py_in == AST__BAD ) {
+                  *px_out = AST__BAD;
+                  *py_out = AST__BAD;
+
+               } else {
+
+/* Get the zero-based integer indices of the grid cell containing the
+   input position. The cell boundaries on the low RA edges are considered
+   to be in the cell. Those on the high RA edges are considered to be part
+   of the neigbouring cell. */
+                  ix = ceil( *px_in - 1.5 );
+                  iy = ceil( *py_in - 1.5 );
+
+/* Get the facet indices and check they are legal. */
+                  fx = ix/nppf;
+                  fy = iy/nppf;
+                  if( fx >= 0 && fx < 5 && fy >= 0 && fy < 5 &&
+                      abs( fx - fy ) <= 1 ) {
+
+/* Get the sum of the zero-based x and y grid indices, plus one. */
+                     s = ix + iy + 1;
+
+/* The bottom left half of the bottom left facet and the top right half
+   of the top right facet are illegal. */
+                     if( s <= nppf || s > n9 ) {
+                        *px_out = AST__BAD;
+                        *py_out = AST__BAD;
+
+/* Other input positions in the bottom left half of the whole-sky map get
+   moved to the top right by adding 2*nppf on each axis. */
+                     } else if( s <= n5 ) {
+                        *px_out = *px_in + n2;
+                        *py_out = *py_in + n2;
+
+/* Other input positions in the rop right half of the whole-sky map get
+   moved to the bottom left by subtracting 2*nppf on each axis. */
+                     } else {
+                        *px_out = *px_in - n2;
+                        *py_out = *py_in - n2;
+                     }
+
+                  } else {
+                     *px_out = AST__BAD;
+                     *py_out = AST__BAD;
+                  }
+               }
+            }
+
+/* Transforming from HPX12 to XPHN */
+         } else if( map->type == AST__XPHN ){
+
+            for ( point = 0; point < npoint; point++,
+                  px_in++,py_in++,px_out++,py_out++ ) {
+
+               if ( *px_in == AST__BAD || *py_in == AST__BAD ) {
+                  *px_out = AST__BAD;
+                  *py_out = AST__BAD;
+               } else {
+
+/* Get the zero-based integer indices of the grid cell containing the
+   input position. The cell boundaries on the low RA edges are considered
+   to be in the cell. Those on the high RA edges are considered to be part
+   of the neigbouring cell. */
+                  ix = ceil( *px_in - 1.5 );
+                  iy = ceil( *py_in - 1.5 );
+
+/* Get the facet indices and check they are legal. */
+                  fx = ix/nppf;
+                  fy = iy/nppf;
+                  if( fx >= 0 && fx < 5 && fy >= 0 && fy < 5 &&
+                      abs( fx - fy ) <= 1 ) {
+
+/* Get the sum of the zero-based x and y grid indices, plus one. */
+                     s = ix + iy + 1;
+
+/* The bottom left half of the bottom left facet and the top right half
+   of the top right facet are illegal. */
+                     if( s <= nppf || s > n9 ) {
+                        *px_out = AST__BAD;
+                        *py_out = AST__BAD;
+/* Gore 2 */
+                     } else if( s <= n3 ) {
+                        *px_out = n2 + *px_in;
+                        *py_out = *py_in;
+/* Gore 3 */
+                     } else if( s <= n5 ) {
+                        *px_out = n5 + 1.0 - *py_in;
+                        *py_out = nppf + *px_in;
+/* Gore 0 */
+                     } else if( s <= n7 ) {
+                        *px_out = n4 + 1.0 - *px_in;
+                        *py_out = n6 + 1.0 - *py_in;
+/* Gore 1 */
+                     } else {
+                        *px_out = *py_in - n3;
+                        *py_out = n5 + 1.0 - *px_in;
+                     }
+
+                  } else {
+                     *px_out = AST__BAD;
+                     *py_out = AST__BAD;
+                  }
+               }
+            }
+
+/* Transforming from HPX12 to XPHS */
+         } else if( map->type == AST__XPHS ){
+
+            for ( point = 0; point < npoint; point++,
+                  px_in++,py_in++,px_out++,py_out++ ) {
+
+               if ( *px_in == AST__BAD || *py_in == AST__BAD ) {
+                  *px_out = AST__BAD;
+                  *py_out = AST__BAD;
+               } else {
+
+/* Get the zero-based integer indices of the grid cell containing the
+   input position. The cell boundaries on the low RA edges are considered
+   to be in the cell. Those on the high RA edges are considered to be part
+   of the neigbouring cell. */
+                  ix = ceil( *px_in - 1.5 );
+                  iy = ceil( *py_in - 1.5 );
+
+/* Get the facet indices and check they are legal. */
+                  fx = ix/nppf;
+                  fy = iy/nppf;
+                  if( fx >= 0 && fx < 5 && fy >= 0 && fy < 5 &&
+                      abs( fx - fy ) <= 1 ) {
+
+/* Get the sum of the x and y grid indices, plus one. */
+                     s = ix + iy + 1;
+
+/* The bottom left half of the bottom left facet and the top right half
+   of the top right facet are illegal. */
+                     if( s <= nppf || s > n9 ) {
+                        *px_out = AST__BAD;
+                        *py_out = AST__BAD;
+/* Gore 2 */
+                     } else if( s <= n3 ) {
+                        *px_out = n2 + *py_in;
+                        *py_out = n4 + 1.0 - *px_in;
+/* Gore 3 */
+                     } else if( s <= n5 ) {
+                        *px_out = n5 + 1.0 - *px_in;
+                        *py_out = n3 + 1.0 - *py_in;
+/* Gore 0 */
+                     } else if( s <= n7 ) {
+                        *px_out = n4 + 1.0 - *py_in;
+                        *py_out = *px_in - n2;
+/* Gore 1 */
+                     } else {
+                        *px_out = *px_in - n3;
+                        *py_out = *py_in - nppf;
+                     }
+
+                  } else {
+                     *px_out = AST__BAD;
+                     *py_out = AST__BAD;
+                  }
+               }
+            }
+
+/* Unknown projection code */
+         } else if( astOK ) {
+            astError( AST__INTER, "astTransform(%s): Invalid projection type "
+                      "encountered (%d) (internal programming error).", status,
+                      astGetClass(this), map->type );
+         }
+      }
+   }
+
+/* Return a pointer to the output PointSet. */
+   return result;
+}
+
+/* Functions which access class attributes. */
+/* ---------------------------------------- */
+/* Implement member functions to access the attributes associated with
+   this class using the macros defined for this purpose in the
+   "object.h" file. For a description of each attribute, see the class
+   interface (in the associated .h file). */
+
+/* Copy constructor. */
+/* ----------------- */
+/* No copy constructor is needed, as a byte-by-byte copy suffices. */
+
+/* Destructor. */
+/* ----------- */
+/* No destructor is needed as no memory, etc. needs freeing. */
+
+/* Dump function. */
+/* -------------- */
+static void Dump( AstObject *this_object, AstChannel *channel, int *status ) {
+/*
+*  Name:
+*     Dump
+
+*  Purpose:
+*     Dump function for XphMap objects.
+
+*  Type:
+*     Private function.
+
+*  Synopsis:
+*     void Dump( AstObject *this, AstChannel *channel, int *status )
+
+*  Description:
+*     This function implements the Dump function which writes out data
+*     for the XphMap class to an output Channel.
+
+*  Parameters:
+*     this
+*        Pointer to the XphMap whose data are being written.
+*     channel
+*        Pointer to the Channel to which the data are being written.
+*     status
+*        Pointer to the inherited status variable.
+*/
+
+/* Local Variables: */
+   AstXphMap *this;             /* Pointer to the XphMap structure */
+
+/* Check the global error status. */
+   if ( !astOK ) return;
+
+/* Obtain a pointer to the XphMap structure. */
+   this = (AstXphMap *) this_object;
+
+/* Write out values representing the instance variables for the
+   XphMap class.  Accompany these with appropriate comment strings,
+   possibly depending on the values being written.*/
+
+   astWriteInt( channel, "Order", 1, 1, this->order, "HEALPix order" );
+   astWriteString( channel, "Type", 1, 1, proj_name[this->type],
+                   proj_comm[this->type]);
+}
+
+/* Standard class functions. */
+/* ========================= */
+/* Implement the astIsAXphMap and astCheckXphMap functions using the macros
+   defined for this purpose in the "object.h" header file. */
+astMAKE_ISA(XphMap,Mapping)
+astMAKE_CHECK(XphMap)
+
+AstXphMap *astXphMap_( int order, int type, const char *options, int *status, ...) {
+/*
+*+
+*  Name:
+*     astXphMap
+
+*  Purpose:
+*     Create an XphMap.
+
+*  Type:
+*     Public function.
+
+*  Synopsis:
+*     #include "xphmap.h"
+*     AstXphMap *astXphMap( int order, int type, const char *options, ... )
+
+*  Class Membership:
+*     XphMap constructor.
+
+*  Description:
+*     This function creates a new XphMap and optionally initialises its
+*     attributes.
+*
+*     The XphMap class implements a Mapping between grid coordinates
+*     within different types of HEALPix projection: The available types
+*     are :
+*
+*     - "HPX0":  An HPX projection centred on RA=0h.
+*     - "HPX12": An HPX projection centred on RA=12h.
+*     - "XPHN":  An XPH ("Butterfly") projection centred on the
+*                 north pole.
+*     - "XPHS":  An XPH ("Butterfly") projection centred on the
+*                south pole.
+*
+*     The HPX projection is described in "Mapping on the HEALPix grid"
+*     by Calabretta and Roukema, A&A, 2005. The XPH projection is
+*     described in "Representing the 'butterfly' projection in FITS -
+*     projection code XPH" by Calabretta and Lowe, PASA, 2018.
+*
+*     The forward transformation of an XphMap transforms from grid
+*     coordinates within the projection type specified by argument
+*     "type" into grid coordinates within an HPX0 projection.
+
+*  Parameters:
+*     order
+*        The HEALPix order of the HPX transformation.
+*     type
+*        The type of projection corresponding to the inputs of the
+*        XphMap. This can be:
+*        - AST__HPX0: A basic HPX projection (centred on RA=0h)
+*        - AST__HPX12: An HPX projection centred on RA=12h.
+*        - AST__XPHN: An XPH ("Butterfly") projection centred on the
+*                     north pole.
+*        - AST__XPHS: An XPH ("Butterfly") projection centred on the
+*                     south pole.
+*     options
+*        Pointer to a null-terminated string containing an optional
+*        comma-separated list of attribute assignments to be used for
+*        initialising the new XphMap. The syntax used is identical to
+*        that for the astSet function and may include "printf" format
+*        specifiers identified by "%" symbols in the normal way.
+*     ...
+*        If the "options" string contains "%" format specifiers, then
+*        an optional list of additional arguments may follow it in
+*        order to supply values to be substituted for these
+*        specifiers. The rules for supplying these are identical to
+*        those for the astSet function (and for the C "printf"
+*        function).
+
+*  Returned Value:
+*     astXphMap()
+*        A pointer to the new XphMap.
+
+*  Notes:
+*     - A null Object pointer (AST__NULL) will be returned if this
+*     function is invoked with the AST error status set, or if it
+*     should fail for any reason.
+
+*  Status Handling:
+*     The protected interface to this function includes an extra
+*     parameter at the end of the parameter list descirbed above. This
+*     parameter is a pointer to the integer inherited status
+*     variable: "int *status".
+
+*-
+*/
+
+/* Local Variables: */
+   astDECLARE_GLOBALS            /* Pointer to thread-specific global data */
+   AstXphMap *new;              /* Pointer to new XphMap */
+   va_list args;                 /* Variable argument list */
+
+/* Get a pointer to the thread specific global data structure. */
+   astGET_GLOBALS(NULL);
+
+/* Check the global status. */
+   if ( !astOK ) return NULL;
+
+/* Initialise the XphMap, allocating memory and initialising the
+   virtual function table as well if necessary. */
+   new = astInitXphMap( NULL, sizeof( AstXphMap ), !class_init, &class_vtab,
+                         "XphMap", order, type );
+
+/* If successful, note that the virtual function table has been
+   initialised. */
+   if ( astOK ) {
+      class_init = 1;
+
+/* Obtain the variable argument list and pass it along with the options string
+   to the astVSet method to initialise the new XphMap's attributes. */
+      va_start( args, status );
+      astVSet( new, options, NULL, args );
+      va_end( args );
+
+/* If an error occurred, clean up by deleting the new object. */
+      if ( !astOK ) new = astDelete( new );
+   }
+
+/* Return a pointer to the new XphMap. */
+   return new;
+}
+
+AstXphMap *astInitXphMap_( void *mem, size_t size, int init,
+                           AstXphMapVtab *vtab, const char *name,
+                           int order, int type, int *status ) {
+/*
+*+
+*  Name:
+*     astInitXphMap
+
+*  Purpose:
+*     Initialise a XphMap.
+
+*  Type:
+*     Protected function.
+
+*  Synopsis:
+*     #include "xphmap.h"
+*     AstXphMap *astInitXphMap( void *mem, size_t size, int init,
+*                               AstXphMapVtab *vtab, const char *name,
+*                               int order, int type )
+
+*  Class Membership:
+*     XphMap initialiser.
+
+*  Description:
+*     This function is provided for use by class implementations to initialise
+*     a new XphMap object. It allocates memory (if necessary) to accommodate
+*     the XphMap plus any additional data associated with the derived class.
+*     It then initialises a XphMap structure at the start of this memory. If
+*     the "init" flag is set, it also initialises the contents of a virtual
+*     function table for a XphMap at the start of the memory passed via the
+*     "vtab" parameter.
+
+*  Parameters:
+*     mem
+*        A pointer to the memory in which the XphMap is to be initialised.
+*        This must be of sufficient size to accommodate the XphMap data
+*        (sizeof(XphMap)) plus any data used by the derived class. If a value
+*        of NULL is given, this function will allocate the memory itself using
+*        the "size" parameter to determine its size.
+*     size
+*        The amount of memory used by the XphMap (plus derived class data).
+*        This will be used to allocate memory if a value of NULL is given for
+*        the "mem" parameter. This value is also stored in the XphMap
+*        structure, so a valid value must be supplied even if not required for
+*        allocating memory.
+*     init
+*        A logical flag indicating if the XphMap's virtual function table is
+*        to be initialised. If this value is non-zero, the virtual function
+*        table will be initialised by this function.
+*     vtab
+*        Pointer to the start of the virtual function table to be associated
+*        with the new XphMap.
+*     name
+*        Pointer to a constant null-terminated character string which contains
+*        the name of the class to which the new object belongs (it is this
+*        pointer value that will subsequently be returned by the astGetClass
+*        method).
+*     order
+*        The HEALPix order.
+*     type
+*        The projection type.
+
+*  Returned Value:
+*     A pointer to the new XphMap.
+
+*  Notes:
+*     -  A null pointer will be returned if this function is invoked with the
+*     global error status set, or if it should fail for any reason.
+*-
+*/
+
+/* Local Variables: */
+   AstXphMap *new;              /* Pointer to new XphMap */
+
+/* Check the global status. */
+   if ( !astOK ) return NULL;
+
+/* If necessary, initialise the virtual function table. */
+   if ( init ) astInitXphMapVtab( vtab, name );
+
+/* Initialise. */
+   new = NULL;
+
+
+/* Validate inputs */
+   if( order < 0 || order > AST__MXORDHPX ) {
+      astError( AST__INTER, "astInitXphMap(%s): Invalid order supplied "
+                "(%d) (internal programming error).", status, name, order );
+   } else if( type < 0 || type > AST__MXPRJHPX ) {
+      astError( AST__INTER, "astInitXphMap(%s): Invalid projection type "
+                "supplied (%d) (internal programming error).", status,
+                 name, type );
+   }
+
+/* Initialise a Mapping structure (the parent class) as the first component
+   within the XphMap structure, allocating memory if necessary. Specify that
+   the Mapping should be defined in both the forward and inverse directions. */
+   new = (AstXphMap *) astInitMapping( mem, size, 0, (AstMappingVtab *) vtab,
+                                       name, 2, 2, 1, 1 );
+   if ( astOK ) {
+
+/* Initialise the XphMap data. */
+/* ---------------------------- */
+      new->order = order;
+      new->type = type;
+
+/* If an error occurred, clean up by deleting the new XphMap. */
+      if ( !astOK ) new = astDelete( new );
+   }
+
+/* Return a pointer to the new XphMap. */
+   return new;
+}
+
+AstXphMap *astLoadXphMap_( void *mem, size_t size, AstXphMapVtab *vtab,
+                           const char *name, AstChannel *channel, int *status ) {
+/*
+*+
+*  Name:
+*     astLoadXphMap
+
+*  Purpose:
+*     Load a XphMap.
+
+*  Type:
+*     Protected function.
+
+*  Synopsis:
+*     #include "xphmap.h"
+*     AstXphMap *astLoadXphMap( void *mem, size_t size, AstXphMapVtab *vtab,
+*                               const char *name, AstChannel *channel )
+
+*  Class Membership:
+*     XphMap loader.
+
+*  Description:
+*     This function is provided to load a new XphMap using data read
+*     from a Channel. It first loads the data used by the parent class
+*     (which allocates memory if necessary) and then initialises a
+*     XphMap structure in this memory, using data read from the input
+*     Channel.
+*
+*     If the "init" flag is set, it also initialises the contents of a
+*     virtual function table for a XphMap at the start of the memory
+*     passed via the "vtab" parameter.
+
+
+*  Parameters:
+*     mem
+*        A pointer to the memory into which the XphMap is to be
+*        loaded.  This must be of sufficient size to accommodate the
+*        XphMap data (sizeof(XphMap)) plus any data used by derived
+*        classes. If a value of NULL is given, this function will
+*        allocate the memory itself using the "size" parameter to
+*        determine its size.
+*     size
+*        The amount of memory used by the XphMap (plus derived class
+*        data).  This will be used to allocate memory if a value of
+*        NULL is given for the "mem" parameter. This value is also
+*        stored in the XphMap structure, so a valid value must be
+*        supplied even if not required for allocating memory.
+*
+*        If the "vtab" parameter is NULL, the "size" value is ignored
+*        and sizeof(AstXphMap) is used instead.
+*     vtab
+*        Pointer to the start of the virtual function table to be
+*        associated with the new XphMap. If this is NULL, a pointer
+*        to the (static) virtual function table for the XphMap class
+*        is used instead.
+*     name
+*        Pointer to a constant null-terminated character string which
+*        contains the name of the class to which the new object
+*        belongs (it is this pointer value that will subsequently be
+*        returned by the astGetClass method).
+*
+*        If the "vtab" parameter is NULL, the "name" value is ignored
+*        and a pointer to the string "XphMap" is used instead.
+
+*  Returned Value:
+*     A pointer to the new XphMap.
+
+*  Notes:
+*     - A null pointer will be returned if this function is invoked
+*     with the global error status set, or if it should fail for any
+*     reason.
+*-
+*/
+
+/* Local Variables: */
+   AstXphMap *new;              /* Pointer to the new XphMap */
+   const char *text;            /* Text for string-valued attribute */
+   astDECLARE_GLOBALS           /* Pointer to thread-specific global data */
+
+/* Initialise. */
+   new = NULL;
+
+/* Check the global error status. */
+   if ( !astOK ) return new;
+
+/* Get a pointer to the thread specific global data structure. */
+   astGET_GLOBALS(channel);
+
+/* If a NULL virtual function table has been supplied, then this is
+   the first loader to be invoked for this XphMap. In this case the
+   XphMap belongs to this class, so supply appropriate values to be
+   passed to the parent class loader (and its parent, etc.). */
+   if ( !vtab ) {
+      size = sizeof( AstXphMap );
+      vtab = &class_vtab;
+      name = "XphMap";
+
+/* If required, initialise the virtual function table for this class. */
+      if ( !class_init ) {
+         astInitXphMapVtab( vtab, name );
+         class_init = 1;
+      }
+   }
+
+/* Invoke the parent class loader to load data for all the ancestral
+   classes of the current one, returning a pointer to the resulting
+   partly-built XphMap. */
+   new = astLoadMapping( mem, size, (AstMappingVtab *) vtab, name,
+                         channel );
+
+   if ( astOK ) {
+
+/* Read input data. */
+/* ================ */
+/* Request the input Channel to read all the input data appropriate to
+   this class into the internal "values list". */
+      astReadClassData( channel, "XphMap" );
+
+/* Now read each individual data item from this list and use it to
+   initialise the appropriate instance variable(s) for this class. */
+      new->order = astReadInt( channel, "order", 19 );
+      text = astReadString( channel, "type", proj_name[AST__HPX12] );
+
+/* COnvert the projection name into an integer projection identifier. */
+      for( new->type = 0; new->type <= AST__MXPRJHPX; new->type++ ) {
+         if( astChrMatch( text, proj_name[new->type] ) ) break;
+      }
+
+/* Report an error if the projection name is unknown. */
+      if( new->type > AST__MXPRJHPX && astOK ) {
+         astError( AST__OPT, "astRead(XphMap): Illegal value '%s' supplied "
+                   "for the XphMap component 'Type'.", status, text );
+      }
+
+/* If an error occurred, clean up by deleting the new XphMap. */
+      if ( !astOK ) new = astDelete( new );
+   }
+
+/* Return the new XphMap pointer. */
+   return new;
+}
+
+/* Virtual function interfaces. */
+/* ============================ */
+/* These provide the external interface to the virtual functions defined by
+   this class. Each simply checks the global error status and then locates and
+   executes the appropriate member function, using the function pointer stored
+   in the object's virtual function table (this pointer is located using the
+   astMEMBER macro defined in "object.h").
+
+   Note that the member function may not be the one defined here, as it may
+   have been over-ridden by a derived class. However, it should still have the
+   same interface. */
+
+
+
+
+