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stdlib: fix qsort example in manual
* manual/search.texi (Comparison Functions, Array Sort Function): Sort an array of long ints, not doubles, to avoid hassles with NaNs. Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
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@ -35,19 +35,22 @@ second, zero if they are ``equal'', and positive if the first argument
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is ``greater''.
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Here is an example of a comparison function which works with an array of
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numbers of type @code{double}:
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numbers of type @code{long int}:
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@smallexample
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int
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compare_doubles (const void *a, const void *b)
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compare_long_ints (const void *a, const void *b)
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@{
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const double *da = (const double *) a;
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const double *db = (const double *) b;
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const long int *la = a;
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const long int *lb = b;
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return (*da > *db) - (*da < *db);
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return (*la > *lb) - (*la < *lb);
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@}
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@end smallexample
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(The code would have to be more complicated for an array of @code{double},
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to handle NaNs correctly.)
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The header file @file{stdlib.h} defines a name for the data type of
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comparison functions. This type is a GNU extension.
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@ -183,16 +186,16 @@ in the array before making some comparisons. The only way to perform
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a stable sort with @code{qsort} is to first augment the objects with a
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monotonic counter of some kind.
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Here is a simple example of sorting an array of doubles in numerical
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Here is a simple example of sorting an array of @code{long int} in numerical
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order, using the comparison function defined above (@pxref{Comparison
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Functions}):
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@smallexample
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@{
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double *array;
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int size;
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long int *array;
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size_t nmemb;
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@dots{}
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qsort (array, size, sizeof (double), compare_doubles);
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qsort (array, nmemb, sizeof *array, compare_long_ints);
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@}
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@end smallexample
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