GCC 除法截断（舍入问题）
在 Ubuntu Linux 10.04 上使用 GCC，除法后出现不需要的舍入。
我尝试过：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void FormatReading(int temp)
{
double reading = temp / 100;
printf("%f\n",reading); /* displays 226.000000, was expecting 226.60 */
}
int main(void)
{
FormatReading(22660);
return 0;
}
有人建议我尝试：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void FormatReading(int temp)
{
long reading = temp ;
reading = reading / 100;
printf("%3.2ld\n",reading); /* displays 226 */
}
int main(void)
{
FormatReading(22660);
return 0;
}
我也尝试过：
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void FormatReading(int temp)
{
long reading = temp ;
double reading2 = reading / 100;
printf("%3.2f\n",reading2); /* displays 226.00 */
}
int main(void)
{
FormatReading(22660);
return 0;
}
我还以各种方式尝试使用包含 math.h 和编译器标签 -lm 的舍入函数，但没有找到我正在寻找的东西。
非常感谢任何帮助。
此致， 伯特
Using GCC on the Ubuntu Linux 10.04, I have unwanted rounding after a division.
I tried:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void FormatReading(int temp)
{
double reading = temp / 100;
printf("%f\n",reading); /* displays 226.000000, was expecting 226.60 */
}
int main(void)
{
FormatReading(22660);
return 0;
}
It was suggested to me to try:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void FormatReading(int temp)
{
long reading = temp ;
reading = reading / 100;
printf("%3.2ld\n",reading); /* displays 226 */
}
int main(void)
{
FormatReading(22660);
return 0;
}
I also tried:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void FormatReading(int temp)
{
long reading = temp ;
double reading2 = reading / 100;
printf("%3.2f\n",reading2); /* displays 226.00 */
}
int main(void)
{
FormatReading(22660);
return 0;
}
I also tried the round function using include math.h with compiler tag -lm in various ways, but did not find what I was looking for.
Any help greatly appreciated.
Best regards,
Bert
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评论（2）
temp / 100 是一个整数除法 - 将结果分配给 double 不会改变这一点。
temp / 100is an integer division - that you assign the result to a double doesn't change this.您使用的整数除法总是给出整数结果而不是分数，然后将结果分配给双精度数。除以 100.0 而不是 100 即可得到您想要的行为。
You are using integer division which always gives integral results rather than fractions, and then the result is being assigned to a double. Divide by 100.0 instead of 100 to get the behavior you want.