C++ 错误：二进制 % 的无效操作数（有“double”和“double”）
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error: invalid operands to binary % (have 'double' and 'double')
提问by pisfire
I have a program I am writing that lists 100,000 prime numbers. It works fine for 10 numbers, but after so many numbers they turn into negative values. I changed the ints to long ints and that did not change anything, then I changed them to doubles and I get the error listed in the title. What should my variable be? Keep in mind I am still new to programing. I also looked at some previous posts and did not see the answer.
我正在编写一个程序，它列出了 100,000 个素数。它适用于 10 个数字，但在这么多数字之后它们变成负值。我将整数更改为长整数并且没有任何改变，然后我将它们更改为双精度并且我得到了标题中列出的错误。我的变量应该是什么？请记住，我对编程还很陌生。我也看了一些以前的帖子，没有看到答案。
int is_prime(double x,char array[]){
//doesnt use array but I put it in there
double j=2;//divider
for(j=2;j<=pow(x,0.5);j++){
if((x%j==0)){
return(0);
} //isnt prime
}
return(1);// because it is prime.
}
回答by
You can't use a double with the operator, you must have an int.
您不能将 double 与运算符一起使用，您必须有一个 int。
You should: #include <math.h>and then use the fmod function.
您应该：#include <math.h>然后使用 fmod 函数。
if(fmod(x,j)==0)
Full code:
完整代码：
#include <math.h>
int is_prime(double x,char array[]){
//doesnt use array but I put it in there
double j=2;//divider
for(j=2;j<=pow(x,0.5);j++){
if(fmod(x,j)==0){
return(0);
} //isnt prime
}
return(1);// because it is prime.
}
回答by Mark Elliot
You have two options:
您有两个选择：
Stick with the
%operator, then you're required to cast the inputs tointsif(((int)x % (int)j) == 0)Include
math.hand then usefmod:if(fmod(x, j) == 0)
坚持使用
%运算符，然后您需要将输入转换为intsif(((int)x % (int)j) == 0)包括
math.h然后使用fmod：if(fmod(x, j) == 0)
回答by Jon Hanna
Your immediate question can be solved with fmod, but for your purpose of high-value prime numbers, you may be better off looking at a big-integer class, like that at http://sourceforge.net/projects/cpp-bigint/since what you really want is integer mathematics, and using floats might cause problems as things progress.
您的直接问题可以用 解决fmod，但是为了您的高价值素数的目的，您最好查看一个大整数类，例如http://sourceforge.net/projects/cpp-bigint/因为你真正想要的是整数数学，随着事情的进展，使用浮点数可能会导致问题。
