C语言 浮点异常
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Floating point exception
提问by Shelith
I successfully complied this code:
我成功地编译了这段代码：
#include <stdio.h>
#include <math.h>
int q;
int main()
{
srand( time(NULL) );
int n=3;
q=ceil(sqrt(n));
printf("%d\n %d\n", n,q);
if(n == 2)
printf("%d\n is prime", n);
else if(n % 2 == 0.0 || n < 2)
printf("%d\n is not prime", n);
else
{
int x;
for(x = 0; x < q; x++){
if(n % x == 0)
{
printf("%d\n is not prime", n);
return;
}
else
printf("%d\n is prime", n);
}
}
}
But when I run my code I get the following error:
但是当我运行我的代码时，我收到以下错误：
Floating point exception
浮点异常
What does this error mean and how can I fix it?
这个错误是什么意思，我该如何解决？
回答by Matthew Flaschen
It's caused by n % x, when xis 0. You should have x start at 2 instead. You should not use floating point here at all, since you only need integer operations.
它是由n % x, whenx为 0引起的。您应该让 x 从 2 开始。您根本不应该在这里使用浮点数，因为您只需要整数运算。
General notes:
一般注意事项：
- Try to format your code better. Focus on using a consistent style. E.g. you have one else that starts immediately after a if brace (not even a space), and another with a newline in between.
- Don't use globals unless necessary. There is no reason for
qto be global. - Don't return without a value in a non-void (int) function.
- 尝试更好地格式化您的代码。专注于使用一致的风格。例如，您有一个紧跟在 if 大括号（甚至不是空格）之后开始的其他数据，以及另一个中间有换行符的数据。
- 除非必要，否则不要使用全局变量。没有理由
q成为全球性的。 - 不要在非 void (int) 函数中没有值就返回。
回答by realkstrawn93
http://en.wikipedia.org/wiki/Division_by_zero
http://en.wikipedia.org/wiki/Division_by_zero
http://en.wikipedia.org/wiki/Unix_signal#SIGFPE
http://en.wikipedia.org/wiki/Unix_signal#SIGFPE
This should give you a really good idea. Since a modulus is, in its basic sense, division with a remainder, something % 0IS division by zero and as such, will trigger a SIGFPE being thrown.
这应该给你一个非常好的主意。由于模数在其基本意义上是除以余数，因此something % 0被零除，因此将触发 SIGFPE 被抛出。
回答by Andre Holzner
It's caused by n % xwhere x = 0in the first loop iteration. You can't calculate a modulus with respect to 0.
它是由引起的n % x，其中x = 0在第一循环迭代。您无法计算相对于 0 的模数。
