为什么我收到C2059错误？

Question

MS Visual Studio 2012（cl.exe命令行编译器）。为什么我会收到错误（阅读评论）？

// C89
#include<ctype.h>
#include<time.h>
int main(void){
    long int i;
    long int n = 1000;
    clock_t cur_time1 = clock();
    clock_t cur_time2;
    long double secs;   
    for(i = 0; i < n; ++i);
    cur_time2 = clock();
    // Here I get an error C2059
    secs = long double(cur_time2 - cur_time1)/long double(CLOCKS_PER_SEC);  
    printf("For the thousand: %lf sec.\nFor the billion: %lf sec.\n", 
        secs, secs * 1000000);
    getchar();
}

谢谢。

Answer 1

secs = long double(cur_time2 - cur_time1)/long double(CLOCKS_PER_SEC);  

这是生成错误的行，类型转换的正确用法是：

secs = (long double)(cur_time2 - cur_time1)/(long double)CLOCKS_PER_SEC;