#include <stdio.h>
#include <string.h>
#define MAXLINES 5000
char *lineptr[MAXLINES];
int readlines(char *lineptr[], int nlines);
void writelines(char *lineptr[], int nlines);
void qsort(void *lineptr[], int left, int right, int (*comp)(void *, void *));
int numcmp(char *, char *);
int main(int argc, char *argv[])
{
int nlines;
int numeric = 0;
if(argc > 1 && strcmp(argv[1], "-n") == 0)
numeric = 1;
if((nlines = readlines(lineptr, MAXLINES)) >= 0) {
qsort((void **) lineptr, 0, nlines - 1, (int (*)(void *, void *))(numeric ? numcmp : strcmp));
writelines(lineptr, nlines);
return 0;
} else {
printf("input too big to sort\n");
return 1;
}
}
void qsort(void *v[], int left, int right, int(*comp)(void *, void *))
{
int i, last;
void swap(void *v[], int, int);
if(left >= right)
return;
swap(v, left, (left + right) / 2);
last = left;
for(i = left + 1; i <= right; i++)
if((*comp)(v[i], v[left]) < 0)
swap(v, ++last, i);
swap(v, left, last);
qsort(v, left, last - 1, comp);
qsort(v, last + 1, right, comp);
}
这是来自K&amp; R的直接源代码,在章节指针和函数中,这是他们展示的关于函数指针的示例,但我无法编译我调用QSORT的行(第22行)。我明白了:
22 C:\Users\SUZI\Desktop\solutions\Chapter 5\Exercise 5-14\sort.c conditional expression between distinct pointer types `int (*)(char*, char*)' and `int (*)(const char*, const char*)' lacks a cast
22 C:\Users\SUZI\Desktop\solutions\Chapter 5\Exercise 5-14\sort.c invalid conversion from `int (*)(char*, char*)' to `void*'
22 C:\Users\SUZI\Desktop\solutions\Chapter 5\Exercise 5-14\sort.c invalid conversion from `int (*)(const char*, const char*)' to `void*'
答案 0 :(得分:6)
您正在使用ANSI C编译器进行编译,而不是使用古老的K&amp; R C编译器。
错误消息非常清楚,请查看const
不匹配。将函数更改为与qsort函数需要的签名相同,然后将参数转换为内部。
答案 1 :(得分:5)
尝试将第22行更改为:
qsort((void **) lineptr, 0, nlines - 1, (numeric ? (int (*)(void *, void *))numcmp : (int (*)(void *, void *))strcmp));