Bugfix in lookup_1d_functiontable (tables with just one point).

lookup_1d_functiontable now handles the case of a table with a single
point (xp,yp) correctly. It then returns the associated yp for any value of
x. Before this change, it returned NAN for x!=xp and yp for x==xp.

Additionally, the functions lookup_1d_functiontable and
lookup_2d_functiontable now return NAN (not a number) in case the table
doesn't contain any values.

csmApp/csmbase.c

@@ -11,7 +11,7 @@
 /* module: CSM-BASE                                           */
 /* version-number of module: 1.1                              */
 /* author: Götz Pfeiffer                                     */
-/* last modification date: 2008-06-05                         */
+/* last modification date: 2011-08-16                         */
 /* status: tested                                             */
 /*____________________________________________________________*/
 
@@ -137,6 +137,13 @@ Version 0.96:
   Date: 2007-11-14
   * the usage of semaphores can no be disabled by a macro.
     This was needed for better portability.
+
+  Date: 2011-08-16
+  * The functions lookup_1d_functiontable and lookup_2d_functiontable now
+    return NAN (not a number) in case the table doesn't contain any values. 
+  * lookup_1d_functiontable now handles the case of a table with a single
+    point (xp,yp) correctly. It then returns the associated yp for any value of
+    x. Before this change, it returned NAN for x!=xp and yp for x==xp.
 */
 
     /*----------------------------------------------------*/
@@ -303,6 +310,22 @@ Version 0.96:
 #include <stdio.h>
 #include <string.h>
 
+/* math.h for definition of NAN */
+#include <math.h>
+
+/*@ITI________________________________________________________*/
+/*                         Defines                            */
+/*@ET_________________________________________________________*/
+
+      /*................................................*/
+      /*@IL           the NAN number type               */
+      /*................................................*/
+
+#ifndef NAN
+/*! \internal \brief define NAN if it is not yet defined */
+#define NAN (-(0.0/0.0))
+#endif
+
 /*@ITI________________________________________________________*/
 /*                          Types                             */
 /*@ET_________________________________________________________*/
@@ -897,9 +920,12 @@ static double lookup_1d_functiontable(csm_1d_functiontable *ft, double x,
 
 
     if (res==-1) /* error */
-      return(0);
-    if (res== 2) /* exact match */
-      { c= (xcoords->coordinate)[a];
+      return(NAN);
+    if ((res== 2)||(a==b)) /* exact match or table with just a single value */
+      { 
+        /* if the table has just a single value (only one [x,y] pair) we return
+           the corresponding y value. */
+        c= (xcoords->coordinate)[a];
         return( (ycoords->coordinate)[c.index].value );
       };
 
@@ -979,11 +1005,11 @@ static double lookup_2d_functiontable(csm_2d_functiontable *ft,
 
     res= coordinate_lookup_index(xcoords, x, &xia, &xib);
     if (res==-1) /* error */
-      return(0);
+      return(NAN);
 
     res= coordinate_lookup_index(ycoords, y, &yia, &yib);
     if (res==-1) /* error */
-      return(0);
+      return(NAN);
 
     /* res==2 with exact match is currently not treated separately */