NAG Library Manual, Mark 28.6
```/* nag_sort_search_vector (m01fsc) Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
*
* Mark 28.6, 2022.
*/

#include <nag.h>
#include <stdio.h>

#ifdef __cplusplus
extern "C" {
#endif
static Integer NAG_CALL compare(const Nag_Pointer a, const Nag_Pointer b);
#ifdef __cplusplus
}
#endif

int main(void) {
Integer exit_status = 0;
NagError fail;
Pointer match;
double key, *vec = 0;
size_t i, n;

INIT_FAIL(fail);

/* Skip heading in data file */
scanf("%*[^\n]");
printf("nag_sort_search_vector (m01fsc) Example Program Results\n");
/* Read number of points and number to search for */
scanf("%" NAG_UFMT "%lf", &n, &key);
if (n >= 1) {
if (!(vec = NAG_ALLOC(50, double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
} else {
printf("Invalid n.\n");
exit_status = 1;
return exit_status;
}
for (i = 0; i < n; ++i)
scanf("%lf", &vec[i]);
/* nag_sort_search_vector (m01fsc).
* Searches a vector for either the first or last match to a
* given value
*/
if (nag_sort_search_vector((Pointer)&key, (Pointer)vec, n,
(ptrdiff_t)(sizeof(double)), compare,
Nag_Ascending, Nag_First, &match, &fail)) {
printf("Exact match found: ");
if (fail.code != NE_NOERROR) {
printf("Error from nag_sort_search_vector (m01fsc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
printf("First match index: %" NAG_UFMT "\n",
(size_t)((double *)match - vec));
} else {
printf("No exact match found: ");
if (match != NULL)
printf("Nag_First nearest match index = %" NAG_UFMT "\n",
(size_t)((double *)match - vec));
else
printf("No match in the input array\n");
}
END:
NAG_FREE(vec);
return exit_status;
}

static Integer NAG_CALL compare(const Nag_Pointer a, const Nag_Pointer b) {
double x = *((const double *)a);
double y = *((const double *)b);
return (x < y ? -1 : (x == y ? 0 : 1));
}
```