upgrade AST

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diff --git a/ast/grismmap.c b/ast/grismmap.c
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+/*
+*class++
+*  Name:
+*     GrismMap
+
+*  Purpose:
+*     Transform 1-dimensional coordinates using a grism dispersion equation.
+
+*  Constructor Function:
+c     astGrismMap
+f     AST_GRISMMAP
+
+*  Description:
+*     A GrismMap is a specialised form of Mapping which transforms
+*     1-dimensional coordinates using the spectral dispersion equation
+*     described in FITS-WCS paper III "Representation of spectral
+*     coordinates in FITS". This describes the dispersion produced by
+*     gratings, prisms and grisms.
+*
+*     When initially created, the forward transformation of a GrismMap
+*     transforms input "grism parameter" values into output wavelength
+*     values. The "grism parameter" is a dimensionless value which is
+*     linearly related to position on the detector. It is defined in FITS-WCS
+*     paper III as "the offset on the detector from the point of intersection
+*     of the camera axis, measured in units of the effective local length".
+*     The units in which wavelength values are expected or returned is
+*     determined by the values supplied for the GrismWaveR, GrismNRP and
+*     GrismG attribute: whatever units are used for these attributes will
+*     also be used for the wavelength values.
+
+*  Inheritance:
+*     The GrismMap class inherits from the Mapping class.
+
+*  Attributes:
+*     In addition to those attributes common to all Mappings, every
+*     GrismMap also has the following attributes:
+*
+*     - GrismNR: The refractive index at the reference wavelength
+*     - GrismNRP: Rate of change of refractive index with wavelength
+*     - GrismWaveR: The reference wavelength
+*     - GrismAlpha: The angle of incidence of the incoming light
+*     - GrismG: The grating ruling density
+*     - GrismM: The interference order
+*     - GrismEps: The angle between the normal and the dispersion plane
+*     - GrismTheta: Angle between normal to detector plane and reference ray
+
+*  Functions:
+c     The GrismMap class does not define any new functions beyond those
+f     The GrismMap class does not define any new routines beyond those
+*     which are applicable to all Mappings.
+
+*  Copyright:
+*     Copyright (C) 1997-2006 Council for the Central Laboratory of the
+*     Research Councils
+
+*  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 (Starlink)
+
+*  History:
+*     18-JUN-2003 (DSB):
+*        Original version.
+*     10-MAY-2006 (DSB):
+*        Override astEqual.
+*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 GrismMap
+
+
+/*
+*  Name:
+*     MAKE_CLEAR
+
+*  Purpose:
+*     Implement a method to clear an attribute value for a GrismMap.
+
+*  Type:
+*     Private macro.
+
+*  Synopsis:
+*     #include "grismmap.h"
+*     MAKE_CLEAR(class,attribute,component,assign)
+
+*  Class Membership:
+*     Defined by the GrismMap class.
+
+*  Description:
+*     This macro expands to an implementation of a private member function of
+*     the form:
+*
+*        static void Clear<Attribute>( AstGrismMap *this )
+*
+*     and an external interface function of the form:
+*
+*        void astClear<Attribute>_( AstGrismMap *this )
+*
+*     which implement a method for clearing a specified attribute value for
+*     a class. The derived constants stored in the GrismMap structure are
+*     updated after the attribute has been cleared.
+
+*  Parameters:
+*     class
+*        The name (not the type) of the class to which the attribute belongs.
+*     attribute
+*        The name of the attribute to be cleared, as it appears in the function
+*        name (e.g. Label in "astClearLabel").
+*     component
+*        The name of the class structure component that holds the attribute
+*        value.
+*     assign
+*        An expression that evaluates to the value to assign to the component
+*        to clear its value.
+
+*  Notes:
+*     -  To avoid problems with some compilers, you should not leave any white
+*     space around the macro arguments.
+*/
+
+/* Define the macro. */
+#define MAKE_CLEAR(class,attribute,component,assign) \
+\
+/* Private member function. */ \
+/* ------------------------ */ \
+static void Clear##attribute( Ast##class *this, int *status ) { \
+\
+/* Check the global error status. */ \
+   if ( !astOK ) return; \
+\
+/* Report an error if the object has been cloned (i.e. has a reference \
+   count that is greater than one). */ \
+   if( astGetRefCount( this ) > 1 ) { \
+      astError( AST__IMMUT, "astClear(%s): The " #attribute "attribute of " \
+                "the supplied %s cannot be cleared because the %s has " \
+                "been cloned (programming error).", status, \
+                astGetClass(this), astGetClass(this), astGetClass(this) ); \
+\
+/* Otherwise, assign the "clear" value in the structure component. */ \
+   } else { \
+      this->component = (assign); \
+   } \
+\
+/* Update the derived constants. */ \
+   UpdateConstants( this, status ); \
+} \
+\
+/* External interface. */ \
+/* ------------------- */ \
+void astClear##attribute##_( Ast##class *this, int *status ) { \
+\
+/* Check the global error status. */ \
+   if ( !astOK ) return; \
+\
+/* Invoke the required method via the virtual function table. */ \
+   (**astMEMBER(this,class,Clear##attribute))( this, status ); \
+}
+
+/*
+*  Name:
+*     MAKE_SET
+
+*  Purpose:
+*     Implement a method to set an attribute value for a GrismMap.
+
+*  Type:
+*     Private macro.
+
+*  Synopsis:
+*     #include "grismmap.h"
+*     astMAKE_SET(class,attribute,type,component,assign)
+
+*  Class Membership:
+*     Defined by the GrismMap class.
+
+*  Description:
+*     This macro expands to an implementation of a private member function of
+*     the form:
+*
+*        static void Set<Attribute>( AstGrismMap *this, <Type> value )
+*
+*     and an external interface function of the form:
+*
+*        void astSet<Attribute>_( AstGrismMap *this, <Type> value )
+*
+*     which implement a method for setting a specified attribute value for a
+*     GrismMap. The derived constants stored in the GrismMap structure are
+*     updated after the attribute has been cleared.
+
+*  Parameters:
+*      class
+*         The name (not the type) of the class to which the attribute belongs.
+*      attribute
+*         The name of the attribute to be set, as it appears in the function
+*         name (e.g. Label in "astSetLabel").
+*      type
+*         The C type of the attribute.
+*      component
+*         The name of the class structure component that holds the attribute
+*         value.
+*      assign
+*         An expression that evaluates to the value to be assigned to the
+*         component.
+
+*  Notes:
+*     - To avoid problems with some compilers, you should not leave
+*     any white space around the macro arguments.
+*/
+
+/* Define the macro. */
+#define MAKE_SET(class,attribute,type,component,assign) \
+\
+/* Private member function. */ \
+/* ------------------------ */ \
+static void Set##attribute( Ast##class *this, type value, int *status ) { \
+\
+/* Check the global error status. */ \
+   if ( !astOK ) return; \
+\
+/* Report an error if the object has been cloned (i.e. has a reference \
+   count that is greater than one). */ \
+   if( astGetRefCount( this ) > 1 ) { \
+      astError( AST__IMMUT, "astSet(%s): The " #attribute "attribute of " \
+                "the supplied %s cannot be changed because the %s has " \
+                "been cloned (programming error).", status, \
+                astGetClass(this), astGetClass(this), astGetClass(this) ); \
+\
+/* Otherwise, store the new value in the structure component. */ \
+   } else { \
+      this->component = (assign); \
+   } \
+\
+/* Update the derived constants. */ \
+   UpdateConstants( this, status ); \
+} \
+\
+/* External interface. */ \
+/* ------------------- */ \
+void astSet##attribute##_( Ast##class *this, type value, int *status ) { \
+\
+/* Check the global error status. */ \
+   if ( !astOK ) return; \
+\
+/* Invoke the required method via the virtual function table. */ \
+   (**astMEMBER(this,class,Set##attribute))( this, value, status ); \
+}
+
+
+/* Include files. */
+/* ============== */
+/* Interface definitions. */
+/* ---------------------- */
+
+#include "globals.h"             /* Thread-safe global data access */
+#include "error.h"               /* Error reporting facilities */
+#include "memory.h"              /* Memory management 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 "unitmap.h"             /* Unit Mappings */
+#include "channel.h"             /* I/O channels */
+#include "zoommap.h"             /* ZoomMap interface */
+#include "winmap.h"              /* WinMap interface */
+#include "grismmap.h"            /* Interface definition for this class */
+
+/* Error code definitions. */
+/* ----------------------- */
+#include "ast_err.h"             /* AST error codes */
+
+/* C header files. */
+/* --------------- */
+#include <ctype.h>
+#include <float.h>
+#include <math.h>
+#include <stdarg.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <limits.h>
+#include <string.h>
+
+/* Macros which return the maximum and minimum of two values. */
+#define MAX(aa,bb) ((aa)>(bb)?(aa):(bb))
+#define MIN(aa,bb) ((aa)<(bb)?(aa):(bb))
+
+/* Module Variables. */
+/* ================= */
+
+/* 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 * );
+static const char *(* parent_getattrib)( AstObject *, const char *, int * );
+static int (* parent_testattrib)( AstObject *, const char *, int * );
+static void (* parent_clearattrib)( AstObject *, const char *, int * );
+static void (* parent_setattrib)( AstObject *, const char *, 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; \
+   globals->GetAttrib_Buff[ 0 ] = 0;
+
+/* Create the function that initialises global data for this module. */
+astMAKE_INITGLOBALS(GrismMap)
+
+/* Define macros for accessing each item of thread specific global data. */
+#define class_init astGLOBAL(GrismMap,Class_Init)
+#define class_vtab astGLOBAL(GrismMap,Class_Vtab)
+#define getattrib_buff astGLOBAL(GrismMap,GetAttrib_Buff)
+
+
+
+/* If thread safety is not needed, declare and initialise globals at static
+   variables. */
+#else
+
+static char getattrib_buff[ 101 ];
+
+
+/* Define the class virtual function table and its initialisation flag
+   as static variables. */
+static AstGrismMapVtab 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. */
+AstGrismMap *astGrismMapId_( const char *, ... );
+
+/* Prototypes for Private Member Functions. */
+/* ======================================== */
+static AstPointSet *Transform( AstMapping *, AstPointSet *, int, AstPointSet *, int * );
+static const char *GetAttrib( AstObject *, const char *, int * );
+static AstMapping *CanMerge( AstMapping *, int, AstMapping *, int, int * );
+static int MapMerge( AstMapping *, int, int, int *, AstMapping ***, int **, int * );
+static int TestAttrib( AstObject *, const char *, int * );
+static void ClearAttrib( AstObject *, const char *, int * );
+static void Dump( AstObject *, AstChannel *, int * );
+static int Equal( AstObject *, AstObject *, int * );
+static void SetAttrib( AstObject *, const char *, int * );
+static void UpdateConstants( AstGrismMap *, int * );
+
+static double GetGrismNR( AstGrismMap *, int * );
+static int TestGrismNR( AstGrismMap *, int * );
+static void ClearGrismNR( AstGrismMap *, int * );
+static void SetGrismNR( AstGrismMap *, double, int * );
+
+static double GetGrismNRP( AstGrismMap *, int * );
+static int TestGrismNRP( AstGrismMap *, int * );
+static void ClearGrismNRP( AstGrismMap *, int * );
+static void SetGrismNRP( AstGrismMap *, double, int * );
+
+static double GetGrismWaveR( AstGrismMap *, int * );
+static int TestGrismWaveR( AstGrismMap *, int * );
+static void ClearGrismWaveR( AstGrismMap *, int * );
+static void SetGrismWaveR( AstGrismMap *, double, int * );
+
+static double GetGrismAlpha( AstGrismMap *, int * );
+static int TestGrismAlpha( AstGrismMap *, int * );
+static void ClearGrismAlpha( AstGrismMap *, int * );
+static void SetGrismAlpha( AstGrismMap *, double, int * );
+
+static double GetGrismG( AstGrismMap *, int * );
+static int TestGrismG( AstGrismMap *, int * );
+static void ClearGrismG( AstGrismMap *, int * );
+static void SetGrismG( AstGrismMap *, double, int * );
+
+static int GetGrismM( AstGrismMap *, int * );
+static int TestGrismM( AstGrismMap *, int * );
+static void ClearGrismM( AstGrismMap *, int * );
+static void SetGrismM( AstGrismMap *, int, int * );
+
+static double GetGrismEps( AstGrismMap *, int * );
+static int TestGrismEps( AstGrismMap *, int * );
+static void ClearGrismEps( AstGrismMap *, int * );
+static void SetGrismEps( AstGrismMap *, double, int * );
+
+static double GetGrismTheta( AstGrismMap *, int * );
+static int TestGrismTheta( AstGrismMap *, int * );
+static void ClearGrismTheta( AstGrismMap *, int * );
+static void SetGrismTheta( AstGrismMap *, double, int * );
+
+/* Member functions. */
+/* ================= */
+static AstMapping *CanMerge( AstMapping *map1, int inv1, AstMapping *map2,
+                             int inv2, int *status ){
+/*
+*
+*  Name:
+*     CanMerge
+
+*  Purpose:
+*     Checks if two GrismMaps can be merged.
+
+*  Type:
+*     Private function.
+
+*  Synopsis:
+*     #include "grismmap.h"
+*     AstMapping *CanMerge( AstMapping *map1, int inv1, AstMapping *map2,
+*                           int inv2, int *status )
+
+*  Class Membership:
+*     GrismMap internal utility function.
+
+*  Description:
+*     This function checks the two supplied Mappings to see if they can
+*     be merged into a single Mapping. One of the two Mappings should be
+*     a GrismMap. If they can be merged, the Merged Mapping is returned
+*     as the function value. Otherwise NULL is returned.
+
+*  Parameters:
+*     map1
+*        A pointer to the first mapping.
+*     map2
+*        A pointer to the second mapping.
+*     inv1
+*        The invert flag to use with the first mapping.
+*     inv2
+*        The invert flag to use with the second mapping.
+*     status
+*        Pointer to the inherited status variable.
+
+*  Returned Value:
+*     A pointer to the merged Mapping if the supplied Mappings can be merged,
+*     NULL otherwise.
+
+*/
+
+/* Local Variables: */
+   AstGrismMap *gmap2;        /* Pointer to second GrismMap */
+   AstGrismMap *gmap;         /* Pointer to first GrismMap */
+   AstMapping *ret;           /* Returned merged Mapping */
+   double g;                  /* The value of the GrismG attribute */
+   double nrp;                /* The value of the GrismNRP attribute */
+   double waver;              /* The value of the GrismWaveR attribute */
+   double z;                  /* Wavelength scaling */
+   int invert_result;         /* Is "ret" the inverse of the required Mapping? */
+
+/* Initialise the returned value. */
+   ret = NULL;
+
+/* Check the global error status. */
+   if ( !astOK ) return ret;
+
+/* Initialise variables to avoid "used of uninitialised variable"
+   messages from dumb compilers. */
+   gmap = NULL;
+   invert_result = 0;
+
+/* Initialise the zoom factor of the adjacent ZoomMap to indicate
+   that we have not yet found an adjacent ZoomMap. */
+   z = AST__BAD;
+
+/* If the first Mapping is a GrismMap... */
+   if( !strcmp( "GrismMap", astGetClass( map1 ) ) ) {
+      gmap = (AstGrismMap *) map1;
+
+/* If the second Mapping is also a GrismMap, they can be merged into a
+   UnitMap if one GrismMap is the inverse of the other. */
+      if( !strcmp( "GrismMap", astGetClass( map2 ) ) ) {
+         gmap2 = (AstGrismMap *) map2;
+
+/* Check that the two GrismMaps have the same attribute values. */
+         if( astEQUAL( astGetGrismNR( gmap ), astGetGrismNR( gmap2 )) &&
+             astEQUAL( astGetGrismNRP( gmap ), astGetGrismNRP( gmap2 )) &&
+             astEQUAL( astGetGrismWaveR( gmap ), astGetGrismWaveR( gmap2 )) &&
+             astEQUAL( astGetGrismAlpha( gmap ), astGetGrismAlpha( gmap2 )) &&
+             astEQUAL( astGetGrismG( gmap ), astGetGrismG( gmap2 )) &&
+             astGetGrismM( gmap ) != astGetGrismM( gmap2 ) &&
+             astEQUAL( astGetGrismEps( gmap ), astGetGrismEps( gmap2 )) &&
+             astEQUAL( astGetGrismTheta( gmap ), astGetGrismTheta( gmap2 )) ){
+
+/* If so, check that the GrismMaps are applied in opposite senses. If so
+   we can cancel the two GrismMaps, so return a UnitMap. */
+            if( inv1 != inv2 ) ret = (AstMapping *) astUnitMap( 1, "", status );
+         }
+
+/* If the first Mapping is a GrismMap but the second one is not... */
+      } else {
+
+/* We can merge the GrismMap with the second Mapping if the GrismMap has
+   not been inverted (i.e. if the wavelength output produced by the
+   GrismMap is fed as input to the second Mapping), and if the second
+   Mapping is a ZoomMap. */
+         if( !inv1 ) {
+
+/* Indicate that any merged Mapping to be created later will not need to
+   be inverted. */
+            invert_result = 0;
+
+/* See if the second Mapping is a ZoomMap, and if so, get the zoom
+   factor. If the Invert attribute in the ZoomMap is not set to the
+   required value, invert the zoom factor. This gives us the required
+   *forward* transformation. */
+            if( !strcmp( "ZoomMap", astGetClass( map2 ) ) ) {
+               z = astGetZoom( (AstZoomMap *) map2 );
+               if( astGetInvert( map2 ) != inv2 && z != 0.0 ) z = 1.0/z;
+            }
+         }
+      }
+
+/* If the first Mapping is not a GrismMap, but the second one is... */
+   } else if( !strcmp( "GrismMap", astGetClass( map2 ) ) ) {
+      gmap = (AstGrismMap *) map2;
+
+/* We can merge the GrismMap with the first Mapping if the GrismMap has
+   been inverted (i.e. if the wavelength output produced by the first
+   Mapping is fed as input to the inverted GrismMap), and if the first
+   Mapping is a ZoomMap. */
+      if( inv2 ) {
+
+/* It is easier to consider pairs of Mappings in which an un-inverted
+   GrismMap is followed by a ZoomMap (as in the above case). For this
+   reason, we invert the Mappings here, so that the merged Mapping created
+   later will be in the inverse of the required Mapping. Indicate that the
+   merged Mapping will therefore need to be inverted before being returned. */
+         invert_result = 1;
+
+/* See if the first Mapping is a ZoomMap. If so, get the zoom factor. If the
+   Invert attribute in the ZoomMap is not set to the opposite of the required
+   value, invert the zoom factor. This gives us the required *inverse*
+   transformation. */
+         if( !strcmp( "ZoomMap", astGetClass( map1 ) ) ) {
+            z = astGetZoom( (AstZoomMap *) map1 );
+            if( astGetInvert( map1 ) == inv1 && z != 0.0 ) z = 1.0/z;
+         }
+      }
+   }
+
+/* If required, produce the merged Mapping by merging the forward
+   GrismMap with the following ZoomMap (and then invert the
+   resulting Mapping if it is in the wrong direction). */
+   if( !ret && z != AST__BAD && z != 0.0 ) {
+
+/* Ensure we have a forward GrismMap. */
+      ret = astCopy( gmap );
+      astSetInvert( ret, 0 );
+
+/* Get the required GrismMap attribute values. */
+      g = astGetGrismG( ret );
+      nrp = astGetGrismNRP( ret );
+      waver = astGetGrismWaveR( ret );
+
+/* The above code ensures that z is the zoom factor from the wavelength
+   produced by the forward GrismMap to the final (modified) wavelength units.
+   Set the new GrismMap attribute values. GrismG, GrismNRP and GrismWaveR have
+   units of length and are scaled to represent new length units using the
+   zoom factor found above. */
+      g /= z;
+      nrp /= z;
+      waver *= z;
+
+      astSetGrismG( ret, g );
+      astSetGrismNRP( ret, nrp );
+      astSetGrismWaveR( ret, waver );
+
+/* If required invert this GrismMap. */
+      if( invert_result ) astInvert( ret );
+
+   }
+
+/* Return the answer. */
+   return ret;
+}
+
+static void ClearAttrib( AstObject *this_object, const char *attrib, int *status ) {
+/*
+*  Name:
+*     ClearAttrib
+
+*  Purpose:
+*     Clear an attribute value for a GrismMap.
+
+*  Type:
+*     Private function.
+
+*  Synopsis:
+*     #include "grismmap.h"
+*     void ClearAttrib( AstObject *this, const char *attrib, int *status )
+
+*  Class Membership:
+*     GrismMap member function (over-rides the astClearAttrib protected
+*     method inherited from the Mapping class).
+
+*  Description:
+*     This function clears the value of a specified attribute for a
+*     GrismMap, so that the default value will subsequently be used.
+
+*  Parameters:
+*     this
+*        Pointer to the GrismMap.
+*     attrib
+*        Pointer to a null-terminated string specifying the attribute
+*        name.  This should be in lower case with no surrounding white
+*        space.
+*     status
+*        Pointer to the inherited status variable.
+*/
+
+/* Local Variables: */
+   AstGrismMap *this;             /* Pointer to the GrismMap structure */
+
+/* Check the global error status. */
+   if ( !astOK ) return;
+
+/* Obtain a pointer to the GrismMap structure. */
+   this = (AstGrismMap *) this_object;
+
+/* Check the attribute name and clear the appropriate attribute. */
+   if ( !strcmp( attrib, "grismnr" ) ) {
+      astClearGrismNR( this );
+
+   } else if ( !strcmp( attrib, "grismnrp" ) ) {
+      astClearGrismNRP( this );
+
+   } else if ( !strcmp( attrib, "grismwaver" ) ) {
+      astClearGrismWaveR( this );
+
+   } else if ( !strcmp( attrib, "grismalpha" ) ) {
+      astClearGrismAlpha( this );
+
+   } else if ( !strcmp( attrib, "grismg" ) ) {
+      astClearGrismG( this );
+
+   } else if ( !strcmp( attrib, "grismm" ) ) {
+      astClearGrismM( this );
+
+   } else if ( !strcmp( attrib, "grismeps" ) ) {
+      astClearGrismEps( this );
+
+   } else if ( !strcmp( attrib, "grismtheta" ) ) {
+      astClearGrismTheta( this );
+
+/* If the attribute is still not recognised, pass it on to the parent
+   method for further interpretation. */
+   } else {
+      (*parent_clearattrib)( this_object, attrib, status );
+   }
+}
+
+static int Equal( AstObject *this_object, AstObject *that_object, int *status ) {
+/*
+*  Name:
+*     Equal
+
+*  Purpose:
+*     Test if two GrismMaps are equivalent.
+
+*  Type:
+*     Private function.
+
+*  Synopsis:
+*     #include "grismmap.h"
+*     int Equal( AstObject *this, AstObject *that, int *status )
+
+*  Class Membership:
+*     GrismMap 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 GrismMaps are equivalent.
+
+*  Parameters:
+*     this
+*        Pointer to the first Object (a GrismMap).
+*     that
+*        Pointer to the second Object.
+*     status
+*        Pointer to the inherited status variable.
+
+*  Returned Value:
+*     One if the GrismMaps 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: */
+   AstGrismMap *that;
+   AstGrismMap *this;
+   int nin;
+   int nout;
+   int result;
+
+/* Initialise. */
+   result = 0;
+
+/* Check the global error status. */
+   if ( !astOK ) return result;
+
+/* Obtain pointers to the two GrismMap structures. */
+   this = (AstGrismMap *) this_object;
+   that = (AstGrismMap *) that_object;
+
+/* Check the second object is a GrismMap. We know the first is a
+   GrismMap since we have arrived at this implementation of the virtual
+   function. */
+   if( astIsAGrismMap( that ) ) {
+
+/* Get the number of inputs and outputs and check they are the same for both. */
+      nin = astGetNin( this );
+      nout = astGetNout( this );
+      if( astGetNin( that ) == nin && astGetNout( that ) == nout ) {
+
+/* If the Invert flags for the two GrismMaps differ, it may still be possible
+   for them to be equivalent. First compare the GrismMaps if their Invert
+   flags are the same. In this case all the attributes of the two GrismMaps
+   must be identical. */
+         if( astGetInvert( this ) == astGetInvert( that ) ) {
+
+            if( astEQUAL( this->nr, that->nr ) &&
+                astEQUAL( this->nrp, that->nrp ) &&
+                astEQUAL( this->waver, that->waver ) &&
+                astEQUAL( this->alpha, that->alpha ) &&
+                astEQUAL( this->g, that->g ) &&
+                this->m == that->m &&
+                astEQUAL( this->eps, that->eps ) &&
+                astEQUAL( this->theta, that->theta ) &&
+                astEQUAL( this->k1, that->k1 ) &&
+                astEQUAL( this->k2, that->k2 ) &&
+                astEQUAL( this->k3, that->k3 ) ) {
+                result = 1;
+             }
+
+/* If the Invert flags for the two GrismMaps differ, the attributes of the two
+   GrismMaps must be inversely related to each other. */
+         } else {
+
+/* In the specific case of a GrismMap, Invert flags must be equal. */
+            result = 0;
+
+         }
+      }
+   }
+
+/* If an error occurred, clear the result value. */
+   if ( !astOK ) result = 0;
+
+/* Return the result, */
+   return result;
+}
+
+static const char *GetAttrib( AstObject *this_object, const char *attrib, int *status ) {
+/*
+*  Name:
+*     GetAttrib
+
+*  Purpose:
+*     Get the value of a specified attribute for a GrismMap.
+
+*  Type:
+*     Private function.
+
+*  Synopsis:
+*     #include "grismmap.h"
+*     const char *GetAttrib( AstObject *this, const char *attrib, int *status )
+
+*  Class Membership:
+*     GrismMap member function (over-rides the protected astGetAttrib
+*     method inherited from the Mapping class).
+
+*  Description:
+*     This function returns a pointer to the value of a specified
+*     attribute for a GrismMap, formatted as a character string.
+
+*  Parameters:
+*     this
+*        Pointer to the GrismMap.
+*     attrib
+*        Pointer to a null-terminated string containing the name of
+*        the attribute whose value is required. This name should be in
+*        lower case, with all white space removed.
+*     status
+*        Pointer to the inherited status variable.
+
+*  Returned Value:
+*     - Pointer to a null-terminated string containing the attribute
+*     value.
+
+*  Notes:
+*     - The returned string pointer may point at memory allocated
+*     within the GrismMap, or at static memory. The contents of the
+*     string may be over-written or the pointer may become invalid
+*     following a further invocation of the same function or any
+*     modification of the GrismMap. A copy of the string should
+*     therefore be made if necessary.
+*     - 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: */
+   astDECLARE_GLOBALS            /* Pointer to thread-specific global data */
+   AstGrismMap *this;            /* Pointer to the GrismMap structure */
+   const char *result;           /* Pointer value to return */
+   double dval;                  /* Attribute value */
+
+/* Initialise. */
+   result = NULL;
+
+/* Check the global error status. */
+   if ( !astOK ) return result;
+
+/* Get a pointer to the thread specific global data structure. */
+   astGET_GLOBALS(this_object);
+
+/* Obtain a pointer to the GrismMap structure. */
+   this = (AstGrismMap *) this_object;
+
+/* Compare "attrib" with each recognised attribute name in turn,
+   obtaining the value of the required attribute. If necessary, write
+   the value into "getattrib_buff" as a null-terminated string in an appropriate
+   format.  Set "result" to point at the result string. */
+
+   if ( !strcmp( attrib, "grismnr" ) ) {
+      dval = astGetGrismNR( this );
+      if ( astOK ) {
+         (void) sprintf( getattrib_buff, "%.*g", DBL_DIG, dval );
+         result = getattrib_buff;
+      }
+
+   } else if ( !strcmp( attrib, "grismnrp" ) ) {
+      dval = astGetGrismNRP( this );
+      if ( astOK ) {
+         (void) sprintf( getattrib_buff, "%.*g", DBL_DIG, dval );
+         result = getattrib_buff;
+      }
+
+   } else if ( !strcmp( attrib, "grismwaver" ) ) {
+      dval = astGetGrismWaveR( this );
+      if ( astOK ) {
+         (void) sprintf( getattrib_buff, "%.*g", DBL_DIG, dval );
+         result = getattrib_buff;
+      }
+
+   } else if ( !strcmp( attrib, "grismalpha" ) ) {
+      dval = astGetGrismAlpha( this );
+      if ( astOK ) {
+         (void) sprintf( getattrib_buff, "%.*g", DBL_DIG, dval );
+         result = getattrib_buff;
+      }
+
+   } else if ( !strcmp( attrib, "grismg" ) ) {
+      dval = astGetGrismG( this );
+      if ( astOK ) {
+         (void) sprintf( getattrib_buff, "%.*g", DBL_DIG, dval );
+         result = getattrib_buff;
+      }
+
+   } else if ( !strcmp( attrib, "grismm" ) ) {
+      dval = astGetGrismM( this );
+      if ( astOK ) {
+         (void) sprintf( getattrib_buff, "%.*g", DBL_DIG, dval );
+         result = getattrib_buff;
+      }
+
+   } else if ( !strcmp( attrib, "grismeps" ) ) {
+      dval = astGetGrismEps( this );
+      if ( astOK ) {
+         (void) sprintf( getattrib_buff, "%.*g", DBL_DIG, dval );
+         result = getattrib_buff;
+      }
+
+   } else if ( !strcmp( attrib, "grismtheta" ) ) {
+      dval = astGetGrismTheta( this );
+      if ( astOK ) {
+         (void) sprintf( getattrib_buff, "%.*g", DBL_DIG, dval );
+         result = getattrib_buff;
+      }
+
+/* If the attribute name was not recognised, pass it on to the parent
+   method for further interpretation. */
+   } else {
+      result = (*parent_getattrib)( this_object, attrib, status );
+   }
+
+/* Return the result. */
+   return result;
+}
+
+void astInitGrismMapVtab_(  AstGrismMapVtab *vtab, const char *name, int *status ) {
+/*
+*+
+*  Name:
+*     astInitGrismMapVtab
+
+*  Purpose:
+*     Initialise a virtual function table for a GrismMap.
+
+*  Type:
+*     Protected function.
+
+*  Synopsis:
+*     #include "grismmap.h"
+*     void astInitGrismMapVtab( AstGrismMapVtab *vtab, const char *name )
+
+*  Class Membership:
+*     GrismMap vtab initialiser.
+
+*  Description:
+*     This function initialises the component of a virtual function
+*     table which is used by the GrismMap 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 astIsAGrismMap) 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. */
+   vtab->ClearGrismNR = ClearGrismNR;
+   vtab->GetGrismNR = GetGrismNR;
+   vtab->SetGrismNR = SetGrismNR;
+   vtab->TestGrismNR = TestGrismNR;
+
+   vtab->ClearGrismNRP = ClearGrismNRP;
+   vtab->GetGrismNRP = GetGrismNRP;
+   vtab->SetGrismNRP = SetGrismNRP;
+   vtab->TestGrismNRP = TestGrismNRP;
+
+   vtab->ClearGrismWaveR = ClearGrismWaveR;
+   vtab->GetGrismWaveR = GetGrismWaveR;
+   vtab->SetGrismWaveR = SetGrismWaveR;
+   vtab->TestGrismWaveR = TestGrismWaveR;
+
+   vtab->ClearGrismAlpha = ClearGrismAlpha;
+   vtab->GetGrismAlpha = GetGrismAlpha;
+   vtab->SetGrismAlpha = SetGrismAlpha;
+   vtab->TestGrismAlpha = TestGrismAlpha;
+
+   vtab->ClearGrismG = ClearGrismG;
+   vtab->GetGrismG = GetGrismG;
+   vtab->SetGrismG = SetGrismG;
+   vtab->TestGrismG = TestGrismG;
+
+   vtab->ClearGrismM = ClearGrismM;
+   vtab->GetGrismM = GetGrismM;
+   vtab->SetGrismM = SetGrismM;
+   vtab->TestGrismM = TestGrismM;
+
+   vtab->ClearGrismEps = ClearGrismEps;
+   vtab->GetGrismEps = GetGrismEps;
+   vtab->SetGrismEps = SetGrismEps;
+   vtab->TestGrismEps = TestGrismEps;
+
+   vtab->ClearGrismTheta = ClearGrismTheta;
+   vtab->GetGrismTheta = GetGrismTheta;
+   vtab->SetGrismTheta = SetGrismTheta;
+   vtab->TestGrismTheta = TestGrismTheta;
+
+/* 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_clearattrib = object->ClearAttrib;
+   object->ClearAttrib = ClearAttrib;
+   parent_getattrib = object->GetAttrib;
+   object->GetAttrib = GetAttrib;
+   parent_setattrib = object->SetAttrib;
+   object->SetAttrib = SetAttrib;
+   parent_testattrib = object->TestAttrib;
+   object->TestAttrib = TestAttrib;
+
+   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;
+
+/* Declare the class dump, copy and delete functions.*/
+   astSetDump( vtab, Dump, "GrismMap",
+               "Map 1-d coordinates using a spectral disperser" );
+
+/* 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 GrismMap.
+
+*  Type:
+*     Private function.
+
+*  Synopsis:
+*     #include "grismmap.h"
+*     int MapMerge( AstMapping *this, int where, int series, int *nmap,
+*                   AstMapping ***map_list, int **invert_list, int *status )
+
+*  Class Membership:
+*     GrismMap 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 GrismMap 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 GrismMap with a Mapping 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 GrismMap which is to be merged with
+*        its neighbours. This should be a cloned copy of the GrismMap
+*        pointer contained in the array element "(*map_list)[where]"
+*        (see below). This pointer will not be annulled, and the
+*        GrismMap it identifies will not be modified by this function.
+*     where
+*        Index in the "*map_list" array (below) at which the pointer
+*        to the nominated GrismMap 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 *merged_map; /* Merger of two Mappings */
+   int i1;                 /* Lower index of the two GrismMaps being merged */
+   int i2;                 /* Upper index of the two GrismMaps being merged */
+   int i;                  /* Mapping index */
+   int result;             /* Result value to return */
+
+/* Initialise. */
+   result = -1;
+
+/* Check the global error status. */
+   if ( !astOK ) return result;
+
+/* Initialise variables to avoid "used of uninitialised variable"
+   messages from dumb compilers. */
+   i1 = -1;
+   i2 = -1;
+
+/* See if the GrismMap can be merged with the Mappings on either side of it
+   in the list. This can only be done in series for a GrismMap. */
+/* ===================================================================== */
+   if( series ) {
+
+/* Set a flag indicating that we have not yet found a neighbour with which
+   the GrismMap can be merged. */
+      merged_map = NULL;
+
+/* First check the lower neighbour (if any). */
+      if( where > 0 ) {
+         i1 = where - 1;
+         i2 = where;
+         merged_map = CanMerge( ( *map_list )[ i1 ], (* invert_list)[ i1 ],
+                                ( *map_list )[ i2 ], (* invert_list)[ i2 ], status );
+      }
+
+/* If the GrismMap can not be merged with its lower neighbour, check its
+   upper neighbour (if any) in the same way. */
+      if( !merged_map && where < *nmap - 1 ) {
+         i1 = where;
+         i2 = where + 1;
+         merged_map = CanMerge( ( *map_list )[ i1 ], (* invert_list)[ i1 ],
+                                ( *map_list )[ i2 ], (* invert_list)[ i2 ], status );
+      }
+
+/* If either neighbour has passed these checks, replace the pair of
+   Mappings which have been merged with the single merged Mapping returned
+   above. */
+      if( merged_map ) {
+
+/* Annul the two Mappings. */
+         (void) astAnnul( ( *map_list )[ i1 ] );
+         (void) astAnnul( ( *map_list )[ i2 ] );
+
+/* Store a pointer for the merged Mapping in place of the first of the
+   two replaced Mappings. */
+         ( *map_list )[ i1 ] = merged_map;
+         ( *invert_list )[ i1 ] = astGetInvert( merged_map );
+
+/* Shuffle down the remaining Mappings to fill the hole left by the
+   second of the replaced Mappings. */
+         for ( i = i2 + 1; i < *nmap; i++ ) {
+            ( *map_list )[ i - 1 ] = ( *map_list )[ i ];
+            ( *invert_list )[ i - 1 ] = ( *invert_list )[ i ];
+         }
+
+/* Clear the vacated element 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 = i1;
+
+      }
+   }
+
+/* Return the result. */
+   return result;
+}
+
+static void SetAttrib( AstObject *this_object, const char *setting, int *status ) {
+/*
+*  Name:
+*     SetAttrib
+
+*  Purpose:
+*     Set an attribute value for a GrismMap.
+
+*  Type:
+*     Private function.
+
+*  Synopsis:
+*     #include "grismmap.h"
+*     void SetAttrib( AstObject *this, const char *setting )
+
+*  Class Membership:
+*     GrismMap member function (over-rides the astSetAttrib protected
+*     method inherited from the Mapping class).
+
+*  Description:
+*     This function assigns an attribute value for a GrismMap, the
+*     attribute and its value being specified by means of a string of
+*     the form:
+*
+*        "attribute= value "
+*
+*     Here, "attribute" specifies the attribute name and should be in
+*     lower case with no white space present. The value to the right
+*     of the "=" should be a suitable textual representation of the
+*     value to be assigned and this will be interpreted according to
+*     the attribute's data type.  White space surrounding the value is
+*     only significant for string attributes.
+
+*  Parameters:
+*     this
+*        Pointer to the GrismMap.
+*     setting
+*        Pointer to a null-terminated string specifying the new attribute
+*        value.
+*/
+
+/* Local Variables: */
+   AstGrismMap *this;            /* Pointer to the GrismMap structure */
+   double dval;                  /* Attribute value */
+   int len;                      /* Length of setting string */
+   int nc;                       /* Number of characters read by astSscanf */
+
+/* Check the global error status. */
+   if ( !astOK ) return;
+
+/* Obtain a pointer to the GrismMap structure. */
+   this = (AstGrismMap *) this_object;
+
+/* Obtain the length of the setting string. */
+   len = (int) strlen( setting );
+
+/* Test for each recognised attribute in turn, using "astSscanf" to parse
+   the setting string and extract the attribute value (or an offset to
+   it in the case of string values). In each case, use the value set
+   in "nc" to check that the entire string was matched. Once a value
+   has been obtained, use the appropriate method to set it. */
+
+   if (  nc = 0, ( 1 == astSscanf( setting, "grismnr= %lf %n", &dval, &nc ) ) && ( nc >= len ) ) {
+      astSetGrismNR( this, dval );
+
+   } else if (  nc = 0, ( 1 == astSscanf( setting, "grismnrp= %lf %n", &dval, &nc ) ) && ( nc >= len ) ) {
+      astSetGrismNRP( this, dval );
+
+   } else if (  nc = 0, ( 1 == astSscanf( setting, "grismwaver= %lf %n", &dval, &nc ) ) && ( nc >= len ) ) {
+      astSetGrismWaveR( this, dval );
+
+   } else if (  nc = 0, ( 1 == astSscanf( setting, "grismalpha= %lf %n", &dval, &nc ) ) && ( nc >= len ) ) {
+      astSetGrismAlpha( this, dval );
+
+   } else if (  nc = 0, ( 1 == astSscanf( setting, "grismg= %lf %n", &dval, &nc ) ) && ( nc >= len ) ) {
+      astSetGrismG( this, dval );
+
+   } else if (  nc = 0, ( 1 == astSscanf( setting, "grismm= %lf %n", &dval, &nc ) ) && ( nc >= len ) ) {
+      astSetGrismM( this, dval );
+
+   } else if (  nc = 0, ( 1 == astSscanf( setting, "grismeps= %lf %n", &dval, &nc ) ) && ( nc >= len ) ) {
+      astSetGrismEps( this, dval );
+
+   } else if (  nc = 0, ( 1 == astSscanf( setting, "grismtheta= %lf %n", &dval, &nc ) ) && ( nc >= len ) ) {
+      astSetGrismTheta( this, dval );
+
+/* If the attribute is still not recognised, pass it on to the parent
+   method for further interpretation. */
+   } else {
+      (*parent_setattrib)( this_object, setting, status );
+   }
+}
+
+static int TestAttrib( AstObject *this_object, const char *attrib, int *status ) {
+/*
+*  Name:
+*     TestAttrib
+
+*  Purpose:
+*     Test if a specified attribute value is set for a GrismMap.
+
+*  Type:
+*     Private function.
+
+*  Synopsis:
+*     #include "grismmap.h"
+*     int TestAttrib( AstObject *this, const char *attrib, int *status )
+
+*  Class Membership:
+*     GrismMap member function (over-rides the astTestAttrib protected
+*     method inherited from the Mapping class).
+
+*  Description:
+*     This function returns a boolean result (0 or 1) to indicate whether
+*     a value has been set for one of a GrismMap's attributes.
+
+*  Parameters:
+*     this
+*        Pointer to the GrismMap.
+*     attrib
+*        Pointer to a null-terminated string specifying the attribute
+*        name.  This should be in lower case with no surrounding white
+*        space.
+*     status
+*        Pointer to the inherited status variable.
+
+*  Returned Value:
+*     One if a value has been set, otherwise zero.
+
+*  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: */
+   AstGrismMap *this;             /* Pointer to the GrismMap structure */
+   int result;                   /* Result value to return */
+
+/* Initialise. */
+   result = 0;
+
+/* Check the global error status. */
+   if ( !astOK ) return result;
+
+/* Obtain a pointer to the GrismMap structure. */
+   this = (AstGrismMap *) this_object;
+
+/* Check the attribute name and clear the appropriate attribute. */
+   if ( !strcmp( attrib, "grismnr" ) ) {
+      result = astTestGrismNR( this );
+
+   } else if ( !strcmp( attrib, "grismnrp" ) ) {
+      result = astTestGrismNRP( this );
+
+   } else if ( !strcmp( attrib, "grismwaver" ) ) {
+      result = astTestGrismWaveR( this );
+
+   } else if ( !strcmp( attrib, "grismalpha" ) ) {
+      result = astTestGrismAlpha( this );
+
+   } else if ( !strcmp( attrib, "grismg" ) ) {
+      result = astTestGrismG( this );
+
+   } else if ( !strcmp( attrib, "grismm" ) ) {
+      result = astTestGrismM( this );
+
+   } else if ( !strcmp( attrib, "grismeps" ) ) {
+      result = astTestGrismEps( this );
+
+   } else if ( !strcmp( attrib, "grismtheta" ) ) {
+      result = astTestGrismTheta( this );
+
+/* If the attribute is still not recognised, pass it on to the parent
+   method for further interpretation. */
+   } else {
+      result = (*parent_testattrib)( this_object, attrib, status );
+   }
+
+/* Return the result, */
+   return result;
+}
+
+static AstPointSet *Transform( AstMapping *this, AstPointSet *in,
+                               int forward, AstPointSet *out, int *status ) {
+/*
+*  Name:
+*     Transform
+
+*  Purpose:
+*     Apply a GrismMap to transform a set of points.
+
+*  Type:
+*     Private function.
+
+*  Synopsis:
+*     #include "grismmap.h"
+*     AstPointSet *Transform( AstMapping *this, AstPointSet *in,
+*                             int forward, AstPointSet *out, int *status )
+
+*  Class Membership:
+*     GrismMap member function (over-rides the astTransform protected
+*     method inherited from the Mapping class).
+
+*  Description:
+*     This function takes a GrismMap and a set of points encapsulated
+*     in a PointSet and transforms the points so as to apply the
+*     forward or inverse dispersal equation.
+
+*  Parameters:
+*     this
+*        Pointer to the GrismMap.
+*     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 equal 1.
+*     - If an output PointSet is supplied, it must have space for
+*     sufficient number of points (with 1 coordinate value per point)
+*     to accommodate the result. Any excess space will be ignored.
+*/
+
+/* Local Variables: */
+   AstGrismMap *map;             /* Pointer to GrismMap to be applied */
+   AstPointSet *result;          /* Pointer to output PointSet */
+   double **ptr_in;              /* Pointer to input coordinate data */
+   double **ptr_out;             /* Pointer to output coordinate data */
+   double sinbeta;               /* Sin( beta ) (see FITS-WCS paper III) */
+   double value_in;              /* Input coordinate value */
+   int npoint;                   /* Number of points */
+   int point;                    /* Loop counter for points */
+
+/* Check the global error status. */
+   if ( !astOK ) return NULL;
+
+/* Obtain a pointer to the GrismMap. */
+   map = (AstGrismMap *) 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 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;
+
+/* If any of the parameters are undefined fill the output with bad
+   values (if possible). */
+   if( map->k1 == AST__BAD || map->k2 == AST__BAD || map->k3 == AST__BAD ) {
+      if( astOK ) {
+         for ( point = 0; point < npoint; point++ ) {
+            ptr_out[ 0 ][ point ] = AST__BAD;
+         }
+      }
+
+/* Otherwise... */
+   } else {
+
+/* Forward transformation. */
+/* ----------------------- */
+      if ( forward ) {
+
+/* Loop to transform each input point. */
+         for ( point = 0; point < npoint; point++ ) {
+
+/* Extract the input grism parameter value. */
+            value_in = ptr_in[ 0 ][ point ];
+
+/* Check for bad input coordinates and generate a bad result if necessary. */
+            if( value_in == AST__BAD || map->k2 == 0.0 ) {
+               ptr_out[ 0 ][ point ] = AST__BAD;
+
+/* Otherwise, apply the algorithm described in FITS-WCS paper III. */
+            } else {
+               ptr_out[ 0 ][ point ] = ( map->k1 + sin( atan( value_in ) + map->k3 ) )/map->k2;
+            }
+         }
+
+/* Inverse transformation. */
+/* ----------------------- */
+      } else {
+
+/* Loop to transform each input point. */
+         for ( point = 0; point < npoint; point++ ) {
+
+/* Extract the input wavelength value. */
+            value_in = ptr_in[ 0 ][ point ];
+
+/* Check for bad input coordinates and generate a bad result if necessary. */
+            if ( value_in == AST__BAD ) {
+               ptr_out[ 0 ][ point ] = AST__BAD;
+
+/* Otherwise, apply the algorithm described in FITS-WCS paper III. */
+            } else {
+               sinbeta = map->k2*value_in - map->k1;
+               if( sinbeta < -1.0 || sinbeta > 1.0 ) {
+                  ptr_out[ 0 ][ point ] = AST__BAD;
+               } else {
+                  ptr_out[ 0 ][ point ] = tan( asin( sinbeta ) - map->k3 );
+               }
+            }
+         }
+      }
+   }
+
+/* Return a pointer to the output PointSet. */
+   return result;
+}
+
+
+static void UpdateConstants( AstGrismMap *this, int *status ){
+/*
+*  Name:
+*     UpdateConstants
+
+*  Purpose:
+*     Re-calculate the constants used within the transformation.
+
+*  Type:
+*     Private function.
+
+*  Synopsis:
+*     #include "grismmap.h"
+*     void UpdateConstants( AstGrismMap *this, int *status )
+
+*  Class Membership:
+*     GrismMap member function
+
+*  Description:
+*     This function re-calculates the constants used within the
+*     transformation on the basis of the current values of the
+*     GrismMap attributes. It should be called whenever a new value is
+*     set for an attribute, or an attribute is cleared.
+
+*  Parameters:
+*     this
+*        Pointer to the GrismMap.
+*     status
+*        Pointer to the inherited status variable.
+
+*/
+
+/* Local Variables: */
+   double alpha;        /* The current vaue of the GrismAlpha attribute */
+   double coseps;       /* cos( eps ) */
+   double sinalpha;     /* sin( alpha ) */
+   double eps;          /* The current vaue of the GrismEps attribute */
+   double g;            /* The current vaue of the GrismG attribute */
+   double nr;           /* The current vaue of the GrismNR attribute */
+   double nrp;          /* The current vaue of the GrismNRP attribute */
+   double sinbeta_r;    /* sin( beta_r ) */
+   double theta;        /* The current vaue of the GrismTheta attribute */
+   double wave_r;       /* The current vaue of the GrismWaveR attribute */
+   int m;               /* The current vaue of the GrismM attribute */
+
+/* Check the global error status. */
+   if ( !astOK ) return;
+
+/* Get the current attribute values. */
+   nr = astGetGrismNR( this );
+   nrp = astGetGrismNRP( this );
+   wave_r = astGetGrismWaveR( this );
+   alpha = astGetGrismAlpha( this );
+   g = astGetGrismG( this );
+   m = astGetGrismM( this );
+   eps = astGetGrismEps( this );
+   theta = astGetGrismTheta( this );
+
+/* Re-calculate the constants. */
+   coseps = cos( eps );
+   sinalpha = sin( alpha );
+
+   this->k1 = sinalpha*( nr - nrp*wave_r );
+
+   if( coseps != 0.0 ) {
+      this->k2 = ( g*m/coseps ) - nrp*sinalpha;
+
+      sinbeta_r = g*m*wave_r/coseps - nr*sinalpha;
+      if( sinbeta_r < -1.0 || sinbeta_r > 1.0 ) {
+         this->k3 = AST__BAD;
+      } else {
+         this->k3 = asin( sinbeta_r ) + theta;
+      }
+
+   } else {
+      this->k2 = AST__BAD;
+      this->k3 = AST__BAD;
+   }
+
+}
+
+/* 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). */
+
+/*
+*att++
+*  Name:
+*     GrismNR
+
+*  Purpose:
+*     The refractive index at the reference wavelength.
+
+*  Type:
+*     Public attribute.
+
+*  Synopsis:
+*     Double precision.
+
+*  Description:
+*     This attribute holds refractive index of the grism material at the
+*     reference wavelength (given by attribute GrismWaveR). The default
+*     value is 1.0.
+*
+*     Note, the value of this attribute may changed only if the GrismMap
+*     has no more than one reference. That is, an error is reported if the
+*     GrismMap has been cloned, either by including it within another object
+*     such as a CmpMap or FrameSet or by calling the
+c     astClone
+f     AST_CLONE
+*     function.
+
+*  Applicability:
+*     GrismMap
+*        All GrismMaps have this attribute.
+
+*att--
+*/
+MAKE_CLEAR(GrismMap,GrismNR,nr,(AST__BAD))
+astMAKE_GET(GrismMap,GrismNR,double,1.0,( ( this->nr == AST__BAD ) ?
+                                      1.0 : this->nr ))
+MAKE_SET(GrismMap,GrismNR,double,nr,(value) )
+astMAKE_TEST(GrismMap,GrismNR,( this->nr != AST__BAD ))
+
+/*
+*att++
+*  Name:
+*     GrismNRP
+
+*  Purpose:
+*     The rate of change of refractive index with wavelength.
+
+*  Type:
+*     Public attribute.
+
+*  Synopsis:
+*     Double precision.
+
+*  Description:
+*     This attribute holds the rate of change of the refractive index of the
+*     grism material with respect to wavelength at the reference wavelength
+*     (given by attribute GrismWaveR). The default value is 0.0 (the
+*     appropriate value for a pure grating disperser with no prism). The
+*     units of this attribute should be consistent with those of attributes
+*     GrismWaveR and GrismG.
+*
+*     Note, the value of this attribute may changed only if the GrismMap
+*     has no more than one reference. That is, an error is reported if the
+*     GrismMap has been cloned, either by including it within another object
+*     such as a CmpMap or FrameSet or by calling the
+c     astClone
+f     AST_CLONE
+*     function.
+
+*  Applicability:
+*     GrismMap
+*        All GrismMaps have this attribute.
+
+*att--
+*/
+MAKE_CLEAR(GrismMap,GrismNRP,nrp,(AST__BAD))
+astMAKE_GET(GrismMap,GrismNRP,double,0.0,( ( this->nrp == AST__BAD ) ?
+                                      0.0 : this->nrp ))
+MAKE_SET(GrismMap,GrismNRP,double,nrp,(value) )
+astMAKE_TEST(GrismMap,GrismNRP,( this->nrp != AST__BAD ))
+
+/*
+*att++
+*  Name:
+*     GrismWaveR
+
+*  Purpose:
+*     The reference wavelength.
+
+*  Type:
+*     Public attribute.
+
+*  Synopsis:
+*     Double precision.
+
+*  Description:
+*     This attribute holds reference wavelength. The default value is
+*     5000 (Angstrom). The units of this attribute should be consistent with
+*     those of attributes GrismNRP and GrismG.
+*
+*     Note, the value of this attribute may changed only if the GrismMap
+*     has no more than one reference. That is, an error is reported if the
+*     GrismMap has been cloned, either by including it within another object
+*     such as a CmpMap or FrameSet or by calling the
+c     astClone
+f     AST_CLONE
+*     function.
+
+*  Applicability:
+*     GrismMap
+*        All GrismMaps have this attribute.
+
+*att--
+*/
+MAKE_CLEAR(GrismMap,GrismWaveR,waver,(AST__BAD))
+astMAKE_GET(GrismMap,GrismWaveR,double,5000.0,( ( this->waver == AST__BAD ) ?
+                                      5000.0 : this->waver ))
+MAKE_SET(GrismMap,GrismWaveR,double,waver,(value) )
+astMAKE_TEST(GrismMap,GrismWaveR,( this->waver != AST__BAD ))
+
+/*
+*att++
+*  Name:
+*     GrismAlpha
+
+*  Purpose:
+*     The angle of incidence of the incoming light on the grating surface.
+
+*  Type:
+*     Public attribute.
+
+*  Synopsis:
+*     Double precision.
+
+*  Description:
+*     This attribute holds the angle between the incoming light and the
+*     normal to the grating surface, in radians. The default value is 0.
+*
+*     Note, the value of this attribute may changed only if the GrismMap
+*     has no more than one reference. That is, an error is reported if the
+*     GrismMap has been cloned, either by including it within another object
+*     such as a CmpMap or FrameSet or by calling the
+c     astClone
+f     AST_CLONE
+*     function.
+
+*  Applicability:
+*     GrismMap
+*        All GrismMaps have this attribute.
+
+*att--
+*/
+MAKE_CLEAR(GrismMap,GrismAlpha,alpha,(AST__BAD))
+astMAKE_GET(GrismMap,GrismAlpha,double,0.0,( ( this->alpha == AST__BAD ) ?
+                                       0.0 : this->alpha ))
+MAKE_SET(GrismMap,GrismAlpha,double,alpha,(value) )
+astMAKE_TEST(GrismMap,GrismAlpha,( this->alpha != AST__BAD ))
+
+/*
+*att++
+*  Name:
+*     GrismG
+
+*  Purpose:
+*     The grating ruling density.
+
+*  Type:
+*     Public attribute.
+
+*  Synopsis:
+*     Double precision.
+
+*  Description:
+*     This attribute holds the number of grating rulings per unit length.
+*     The unit of length used should be consistent with the units used
+*     for attributes GrismWaveR and GrismNRP. The default value is 0.0.
+*     (the appropriate value for a pure prism disperser with no grating).
+*
+*     Note, the value of this attribute may changed only if the GrismMap
+*     has no more than one reference. That is, an error is reported if the
+*     GrismMap has been cloned, either by including it within another object
+*     such as a CmpMap or FrameSet or by calling the
+c     astClone
+f     AST_CLONE
+*     function.
+
+*  Applicability:
+*     GrismMap
+*        All GrismMaps have this attribute.
+
+*att--
+*/
+MAKE_CLEAR(GrismMap,GrismG,g,(AST__BAD))
+astMAKE_GET(GrismMap,GrismG,double,0.0,( ( this->g == AST__BAD ) ?
+                                      0.0 : this->g ))
+MAKE_SET(GrismMap,GrismG,double,g,(value) )
+astMAKE_TEST(GrismMap,GrismG,( this->g != AST__BAD ))
+
+/*
+*att++
+*  Name:
+*     GrismM
+
+*  Purpose:
+*     The interference order
+
+*  Type:
+*     Public attribute.
+
+*  Synopsis:
+*     Integer.
+
+*  Description:
+*     This attribute holds the interference order being considered.
+*     The default value is 0.
+*
+*     Note, the value of this attribute may changed only if the GrismMap
+*     has no more than one reference. That is, an error is reported if the
+*     GrismMap has been cloned, either by including it within another object
+*     such as a CmpMap or FrameSet or by calling the
+c     astClone
+f     AST_CLONE
+*     function.
+
+*  Applicability:
+*     GrismMap
+*        All GrismMaps have this attribute.
+
+*att--
+*/
+MAKE_CLEAR(GrismMap,GrismM,m,(INT_MAX))
+astMAKE_GET(GrismMap,GrismM,int,0,( ( this->m == INT_MAX ) ?
+                                      0 : this->m ))
+MAKE_SET(GrismMap,GrismM,int,m,(value) )
+astMAKE_TEST(GrismMap,GrismM,( this->m != INT_MAX ))
+
+/*
+*att++
+*  Name:
+*     GrismEps
+
+*  Purpose:
+*      The angle between the normal and the dispersion plane.
+
+*  Type:
+*     Public attribute.
+
+*  Synopsis:
+*     Double precision.
+
+*  Description:
+*     This attribute holds the angle (in radians) between the normal to
+*     the grating or exit prism face, and the dispersion plane. The
+*     dispersion plane is the plane spanned by the incoming and outgoing
+*     ray. The default value is 0.0.
+*
+*     Note, the value of this attribute may changed only if the GrismMap
+*     has no more than one reference. That is, an error is reported if the
+*     GrismMap has been cloned, either by including it within another object
+*     such as a CmpMap or FrameSet or by calling the
+c     astClone
+f     AST_CLONE
+*     function.
+
+*  Applicability:
+*     GrismMap
+*        All GrismMaps have this attribute.
+
+*att--
+*/
+MAKE_CLEAR(GrismMap,GrismEps,eps,(AST__BAD))
+astMAKE_GET(GrismMap,GrismEps,double,0.0,( ( this->eps == AST__BAD ) ?
+                                      0.0 : this->eps ))
+MAKE_SET(GrismMap,GrismEps,double,eps,(value) )
+astMAKE_TEST(GrismMap,GrismEps,( this->eps != AST__BAD ))
+
+/*
+*att++
+*  Name:
+*     GrismTheta
+
+*  Purpose:
+*     Angle between normal to detector plane and reference ray.
+
+*  Type:
+*     Public attribute.
+
+*  Synopsis:
+*     Double precision.
+
+*  Description:
+*     This attribute gives the angle of incidence of light of the
+*     reference wavelength (given by attribute GrismWaveR) onto the
+*     detector. Specifically, it holds the angle (in radians) between
+*     the normal to the detector plane and an incident ray at the reference
+*     wavelength. The default value is 0.0.
+*
+*     Note, the value of this attribute may changed only if the GrismMap
+*     has no more than one reference. That is, an error is reported if the
+*     GrismMap has been cloned, either by including it within another object
+*     such as a CmpMap or FrameSet or by calling the
+c     astClone
+f     AST_CLONE
+*     function.
+
+*  Applicability:
+*     GrismMap
+*        All GrismMaps have this attribute.
+
+*att--
+*/
+MAKE_CLEAR(GrismMap,GrismTheta,theta,(AST__BAD))
+astMAKE_GET(GrismMap,GrismTheta,double,0.0,( ( this->theta == AST__BAD ) ?
+                                      0.0 : this->theta ))
+MAKE_SET(GrismMap,GrismTheta,double,theta,(value) )
+astMAKE_TEST(GrismMap,GrismTheta,( this->theta != AST__BAD ))
+
+/* 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 GrismMap 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 GrismMap class to an output Channel.
+
+*  Parameters:
+*     this
+*        Pointer to the GrismMap 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: */
+   AstGrismMap *this;            /* Pointer to the GrismMap structure */
+   double dval;                  /* Double value */
+   int set;                      /* Attribute value set? */
+
+/* Check the global error status. */
+   if ( !astOK ) return;
+
+/* Obtain a pointer to the GrismMap structure. */
+   this = (AstGrismMap *) this_object;
+
+/* Write out values representing the instance variables for the
+   GrismMap class.  Accompany these with appropriate comment strings,
+   possibly depending on the values being written.*/
+
+/* In the case of attributes, we first use the appropriate (private)
+   Test...  member function to see if they are set. If so, we then use
+   the (private) Get... function to obtain the value to be written
+   out.
+
+   For attributes which are not set, we use the astGet... method to
+   obtain the value instead. This will supply a default value
+   (possibly provided by a derived class which over-rides this method)
+   which is more useful to a human reader as it corresponds to the
+   actual default attribute value.  Since "set" will be zero, these
+   values are for information only and will not be read back. */
+
+   set = TestGrismNR( this, status );
+   dval = set ? GetGrismNR( this, status ) : astGetGrismNR( this );
+   astWriteDouble( channel, "GrmNR", set, 1, dval, "Refractive index at the ref. wavelength" );
+
+   set = TestGrismNRP( this, status );
+   dval = set ? GetGrismNRP( this, status ) : astGetGrismNRP( this );
+   astWriteDouble( channel, "GrmNRP", set, 1, dval, "Rate of change of refractive index" );
+
+   set = TestGrismWaveR( this, status );
+   dval = set ? GetGrismWaveR( this, status ) : astGetGrismWaveR( this );
+   astWriteDouble( channel, "GrmWR", set, 1, dval, "Ref. wavelength" );
+
+   set = TestGrismAlpha( this, status );
+   dval = set ? GetGrismAlpha( this, status ) : astGetGrismAlpha( this );
+   astWriteDouble( channel, "GrmAlp", set, 1, dval, "Angle of incidence of incoming light" );
+
+   set = TestGrismG( this, status );
+   dval = set ? GetGrismG( this, status ) : astGetGrismG( this );
+   astWriteDouble( channel, "GrmG", set, 1, dval, "Grating ruling density" );
+
+   set = TestGrismM( this, status );
+   dval = set ? GetGrismM( this, status ) : astGetGrismM( this );
+   astWriteDouble( channel, "GrmM", set, 1, dval, "The interference order" );
+
+   set = TestGrismEps( this, status );
+   dval = set ? GetGrismEps( this, status ) : astGetGrismEps( this );
+   astWriteDouble( channel, "GrmEps", set, 1, dval, "Angle between grating normal and dispersion plane" );
+
+   set = TestGrismTheta( this, status );
+   dval = set ? GetGrismTheta( this, status ) : astGetGrismTheta( this );
+   astWriteDouble( channel, "GrmTh", set, 1, dval, "Angle between detector normal and reference ray" );
+
+}
+
+
+/* Standard class functions. */
+/* ========================= */
+/* Implement the astIsAGrismMap and astCheckGrismMap functions using the
+   macros defined for this purpose in the "object.h" header file. */
+astMAKE_ISA(GrismMap,Mapping)
+astMAKE_CHECK(GrismMap)
+
+AstGrismMap *astGrismMap_( const char *options, int *status, ...) {
+/*
+*++
+*  Name:
+c     astGrismMap
+f     AST_GRISMMAP
+
+*  Purpose:
+*     Create a GrismMap.
+
+*  Type:
+*     Public function.
+
+*  Synopsis:
+c     #include "grismmap.h"
+c     AstGrismMap *astGrismMap( const char *options, ... )
+f     RESULT = AST_GRISMMAP( OPTIONS, STATUS )
+
+*  Class Membership:
+*     GrismMap constructor.
+
+*  Description:
+*     This function creates a new GrismMap and optionally initialises
+*     its attributes.
+*
+*     A GrismMap is a specialised form of Mapping which transforms
+*     1-dimensional coordinates using the spectral dispersion equation
+*     described in FITS-WCS paper III "Representation of spectral
+*     coordinates in FITS". This describes the dispersion produced by
+*     gratings, prisms and grisms.
+*
+*     When initially created, the forward transformation of a GrismMap
+*     transforms input "grism parameter" values into output wavelength
+*     values. The "grism parameter" is a dimensionless value which is
+*     linearly related to position on the detector. It is defined in FITS-WCS
+*     paper III as "the offset on the detector from the point of intersection
+*     of the camera axis, measured in units of the effective local length".
+*     The units in which wavelength values are expected or returned is
+*     determined by the values supplied for the GrismWaveR, GrismNRP and
+*     GrismG attribute: whatever units are used for these attributes will
+*     also be used for the wavelength values.
+
+*  Parameters:
+c     options
+f     OPTIONS = CHARACTER * ( * ) (Given)
+c        Pointer to a null-terminated string containing an optional
+c        comma-separated list of attribute assignments to be used for
+c        initialising the new GrismMap. The syntax used is identical to
+c        that for the astSet function and may include "printf" format
+c        specifiers identified by "%" symbols in the normal way.
+f        A character string containing an optional comma-separated
+f        list of attribute assignments to be used for initialising the
+f        new GrismMap. The syntax used is identical to that for the
+f        AST_SET routine.
+c     ...
+c        If the "options" string contains "%" format specifiers, then
+c        an optional list of additional arguments may follow it in
+c        order to supply values to be substituted for these
+c        specifiers. The rules for supplying these are identical to
+c        those for the astSet function (and for the C "printf"
+c        function).
+f     STATUS = INTEGER (Given and Returned)
+f        The global status.
+
+*  Returned Value:
+c     astGrismMap()
+f     AST_GRISMMAP = INTEGER
+*        A pointer to the new GrismMap.
+
+*  Notes:
+*     - A null Object pointer (AST__NULL) will be returned if this
+c     function is invoked with the AST error status set, or if it
+f     function is invoked with STATUS set to an error value, or if it
+*     should fail for any reason.
+*--
+*/
+
+/* Local Variables: */
+   astDECLARE_GLOBALS            /* Pointer to thread-specific global data */
+   AstGrismMap *new;             /* Pointer to new GrismMap */
+   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 GrismMap, allocating memory and initialising the
+   virtual function table as well if necessary. */
+   new = astInitGrismMap( NULL, sizeof( AstGrismMap ), !class_init,
+                          &class_vtab, "GrismMap" );
+
+/* 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
+   GrismMap'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 GrismMap. */
+   return new;
+}
+
+AstGrismMap *astGrismMapId_( const char *options, ... ) {
+/*
+*  Name:
+*     astGrismMapId_
+
+*  Purpose:
+*     Create a GrismMap.
+
+*  Type:
+*     Private function.
+
+*  Synopsis:
+*     #include "grismmap.h"
+*     AstGrismMap *astGrismMapId( const char *options, int *status, ... )
+
+*  Class Membership:
+*     GrismMap constructor.
+
+*  Description:
+*     This function implements the external (public) interface to the
+*     astGrismMap constructor function. It returns an ID value (instead
+*     of a true C pointer) to external users, and must be provided
+*     because astGrismMap_ has a variable argument list which cannot be
+*     encapsulated in a macro (where this conversion would otherwise
+*     occur).
+*
+*     The variable argument list also prevents this function from
+*     invoking astGrismMap_ directly, so it must be a re-implementation
+*     of it in all respects, except for the final conversion of the
+*     result to an ID value.
+
+*  Parameters:
+*     As for astGrismMap_.
+*     status
+*        Pointer to the inherited status variable.
+
+*  Returned Value:
+*     The ID value associated with the new GrismMap.
+*/
+
+/* Local Variables: */
+   astDECLARE_GLOBALS            /* Pointer to thread-specific global data */
+   AstGrismMap *new;             /* Pointer to new GrismMap */
+   va_list args;                 /* Variable argument list */
+
+   int *status;                  /* Pointer to inherited status value */
+
+/* Get a pointer to the inherited status value. */
+   status = astGetStatusPtr;
+
+/* Get a pointer to the thread specific global data structure. */
+   astGET_GLOBALS(NULL);
+
+/* Check the global status. */
+   if ( !astOK ) return NULL;
+
+/* Initialise the GrismMap, allocating memory and initialising the
+   virtual function table as well if necessary. */
+   new = astInitGrismMap( NULL, sizeof( AstGrismMap ), !class_init,
+                          &class_vtab, "GrismMap" );
+
+/* 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 GrismMap's
+   attributes. */
+      va_start( args, options );
+      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 an ID value for the new GrismMap. */
+   return astMakeId( new );
+}
+
+AstGrismMap *astInitGrismMap_( void *mem, size_t size, int init,
+                               AstGrismMapVtab *vtab, const char *name, int *status ) {
+/*
+*+
+*  Name:
+*     astInitGrismMap
+
+*  Purpose:
+*     Initialise a GrismMap.
+
+*  Type:
+*     Protected function.
+
+*  Synopsis:
+*     #include "grismmap.h"
+*     AstGrismMap *astInitGrismMap( void *mem, size_t size, int init,
+*                                   AstGrismMapVtab *vtab, const char *name )
+
+*  Class Membership:
+*     GrismMap initialiser.
+
+*  Description:
+*     This function is provided for use by class implementations to initialise
+*     a new GrismMap object. It allocates memory (if necessary) to accommodate
+*     the GrismMap plus any additional data associated with the derived class.
+*     It then initialises a GrismMap 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 GrismMap at the start of the memory passed via the
+*     "vtab" parameter.
+
+*  Parameters:
+*     mem
+*        A pointer to the memory in which the GrismMap is to be initialised.
+*        This must be of sufficient size to accommodate the GrismMap data
+*        (sizeof(GrismMap)) 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 GrismMap (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 GrismMap
+*        structure, so a valid value must be supplied even if not required for
+*        allocating memory.
+*     init
+*        A logical flag indicating if the GrismMap'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 GrismMap.
+*     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).
+
+*  Returned Value:
+*     A pointer to the new GrismMap.
+
+*  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: */
+   AstGrismMap *new;              /* Pointer to new GrismMap */
+
+/* Check the global status. */
+   if ( !astOK ) return NULL;
+
+/* If necessary, initialise the virtual function table. */
+   if ( init ) astInitGrismMapVtab( vtab, name );
+
+/* Initialise. */
+   new = NULL;
+
+/* Initialise a Mapping structure (the parent class) as the first component
+   within the GrismMap structure, allocating memory if necessary. Specify that
+   the Mapping should be defined in both the forward and inverse directions. */
+   new = (AstGrismMap *) astInitMapping( mem, size, 0,
+                                         (AstMappingVtab *) vtab, name,
+                                         1, 1, 1, 1 );
+   if ( astOK ) {
+
+/* Initialise the GrismMap data. */
+/* ---------------------------- */
+      new->nr    = AST__BAD;
+      new->nrp   = AST__BAD;
+      new->waver = AST__BAD;
+      new->alpha = AST__BAD;
+      new->g     = AST__BAD;
+      new->m     = INT_MAX;
+      new->eps   = AST__BAD;
+      new->theta = AST__BAD;
+
+/* Set up the other required derived constants. */
+      UpdateConstants( new, status );
+
+/* If an error occurred, clean up by deleting the new GrismMap. */
+      if ( !astOK ) new = astDelete( new );
+   }
+
+/* Return a pointer to the new GrismMap. */
+   return new;
+}
+
+AstGrismMap *astLoadGrismMap_( void *mem, size_t size,
+                           AstGrismMapVtab *vtab, const char *name,
+                           AstChannel *channel, int *status ) {
+/*
+*+
+*  Name:
+*     astLoadGrismMap
+
+*  Purpose:
+*     Load a GrismMap.
+
+*  Type:
+*     Protected function.
+
+*  Synopsis:
+*     #include "grismmap.h"
+*     AstGrismMap *astLoadGrismMap( void *mem, size_t size,
+*                               AstGrismMapVtab *vtab, const char *name,
+*                               AstChannel *channel )
+
+*  Class Membership:
+*     GrismMap loader.
+
+*  Description:
+*     This function is provided to load a new GrismMap 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
+*     GrismMap 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 GrismMap at the start of the memory
+*     passed via the "vtab" parameter.
+
+
+*  Parameters:
+*     mem
+*        A pointer to the memory into which the GrismMap is to be
+*        loaded.  This must be of sufficient size to accommodate the
+*        GrismMap data (sizeof(GrismMap)) 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 GrismMap (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 GrismMap 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(AstGrismMap) is used instead.
+*     vtab
+*        Pointer to the start of the virtual function table to be
+*        associated with the new GrismMap. If this is NULL, a pointer
+*        to the (static) virtual function table for the GrismMap 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 "GrismMap" is used instead.
+
+*  Returned Value:
+*     A pointer to the new GrismMap.
+
+*  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 Constants: */
+   astDECLARE_GLOBALS            /* Pointer to thread-specific global data */
+#define KEY_LEN 50               /* Maximum length of a keyword */
+
+/* Local Variables: */
+   AstGrismMap *new;             /* Pointer to the new GrismMap */
+
+/* Initialise. */
+   new = NULL;
+
+/* Get a pointer to the thread specific global data structure. */
+   astGET_GLOBALS(channel);
+
+/* Check the global error status. */
+   if ( !astOK ) return new;
+
+/* If a NULL virtual function table has been supplied, then this is
+   the first loader to be invoked for this GrismMap. In this case the
+   GrismMap belongs to this class, so supply appropriate values to be
+   passed to the parent class loader (and its parent, etc.). */
+   if ( !vtab ) {
+      size = sizeof( AstGrismMap );
+      vtab = &class_vtab;
+      name = "GrismMap";
+
+/* If required, initialise the virtual function table for this class. */
+      if ( !class_init ) {
+         astInitGrismMapVtab( 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 GrismMap. */
+   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, "GrismMap" );
+
+/* Now read each individual data item from this list and use it to
+   initialise the appropriate instance variable(s) for this class. */
+
+      new->nr = astReadDouble( channel, "grmnr", AST__BAD );
+      if ( TestGrismNR( new, status ) ) SetGrismNR( new, new->nr, status );
+
+      new->nrp = astReadDouble( channel, "grmnrp", AST__BAD );
+      if ( TestGrismNRP( new, status ) ) SetGrismNRP( new, new->nrp, status );
+
+      new->waver = astReadDouble( channel, "grmwr", AST__BAD );
+      if ( TestGrismWaveR( new, status ) ) SetGrismWaveR( new, new->waver, status );
+
+      new->alpha = astReadDouble( channel, "grmalp", AST__BAD );
+      if ( TestGrismAlpha( new, status ) ) SetGrismAlpha( new, new->alpha, status );
+
+      new->g = astReadDouble( channel, "grmg", AST__BAD );
+      if ( TestGrismG( new, status ) ) SetGrismG( new, new->g, status );
+
+      new->m = astReadInt( channel, "grmm", INT_MAX );
+      if ( TestGrismM( new, status ) ) SetGrismM( new, new->m, status );
+
+      new->eps = astReadDouble( channel, "grmeps", AST__BAD );
+      if ( TestGrismEps( new, status ) ) SetGrismEps( new, new->eps, status );
+
+      new->theta = astReadDouble( channel, "grmth", AST__BAD );
+      if ( TestGrismTheta( new, status ) ) SetGrismTheta( new, new->theta, status );
+
+/* Set up the other required derived constants. */
+      UpdateConstants( new, status );
+   }
+
+/* If an error occurred, clean up by deleting the new GrismMap. */
+   if ( !astOK ) new = astDelete( new );
+
+/* Return the new GrismMap pointer. */
+   return new;
+
+/* Undefine macros local to this function. */
+#undef KEY_LEN
+}
+
+/* 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. */
+
+
+
+
+