K&R has three different versions of qsort, and the ultimate one is supposed
to be like the one in the std library. I'm trying to implement the first,
which is in §4.10.
I think I'm pretty close with this:
void qsort(int v[], int left, int right)
{
int i, last;
void swap(int v[], int i, int j);
if (left >= right)
return;
swap (v, left, (left + right)/2);
last = left;
for (i = left+ 1; i <= right; i++)
if (v[i] < v[left])
swap (v, ++last, i);
swap(v, left, last);
qsort(v, left, last - 1);
qsort(v, last + 1, right);
}
void swap(int v[], int i, int j)
{
int temp;
temp = v[i];
v[i] = v[j];
v[j] = temp;
}
#include <stdio.h>
#define size 9
int main(void)
{
int m[size], i;
for (i=0; i < size; ++ i)
{
m[i] = i - size;
printf(" %d \n ", m[i]);
}
qsort (m[], 0, size - 1);
for (i=0; i < size; ++ i) printf(" %d \n ", m[i]);
return 0;
}
// gcc -o sort c5.c
gcc objects with:
F:\gfortran\sou rce>gcc -o sort c5.c
c5.c: In function 'main':
c5.c:42: error: expected expression before ']' token
If I count correctly, this is the qsort call. I'm not surprised that gcc
objects, as I'm not sure about this syntax at all.
I guess that's question one. The other is how to call the stdlib version
of qsort, whose syntax is given in appdx B5:
void qsort(void *base, size_t n, size_t size,
int (*cmp)(const void *, const void *)
Beautiful night here in New Mexico. I can hear and even smell the state
fair. cheers,
--
We are here and it is now. Further than that, all human knowledge is
moonshine. 3
H. L. Mencken
