is ``greater''.
Here is an example of a comparison function which works with an array of
-numbers of type @code{double}:
+numbers of type @code{long int}:
@smallexample
int
-compare_doubles (const void *a, const void *b)
+compare_long_ints (const void *a, const void *b)
@{
- const double *da = (const double *) a;
- const double *db = (const double *) b;
+ const long int *la = a;
+ const long int *lb = b;
- return (*da > *db) - (*da < *db);
+ return (*la > *lb) - (*la < *lb);
@}
@end smallexample
+(The code would have to be more complicated for an array of @code{double},
+to handle NaNs correctly.)
+
The header file @file{stdlib.h} defines a name for the data type of
comparison functions. This type is a GNU extension.
a stable sort with @code{qsort} is to first augment the objects with a
monotonic counter of some kind.
-Here is a simple example of sorting an array of doubles in numerical
+Here is a simple example of sorting an array of @code{long int} in numerical
order, using the comparison function defined above (@pxref{Comparison
Functions}):
@smallexample
@{
- double *array;
- int size;
+ long int *array;
+ size_t nmemb;
@dots{}
- qsort (array, size, sizeof (double), compare_doubles);
+ qsort (array, nmemb, sizeof *array, compare_long_ints);
@}
@end smallexample