我得到了这个错误，，"vector" was not declared in this scope '' for the following code when I separate in * h and * cpp a file这是main. cpp：

#include <iostream>
#include <math.h>
#include <vector>
#include "functia.h"

using namespace std;

int main()
 {
  vector<double> s(3);
  double b= 4;
  fun(s, b);
  cout<<s[0]<<endl;
  double c= 9;
  fun(s, c);
  cout<<s[0];

  }

functia. h：

void fun(vector<double> & rS, double a)
 {
   rS[0] = a + 3;
   rS[1] = 4;
   rS[2] = 5;
 }

functia.cpp:

#include <iostream>
#include <math.h>
#include<vector>

using namespace std;

void fun(vector<double> &, double );