"vector" was not declared in this scope

Question

I got this error ,,"vector" was not declared in this scope'' for the following code when I separate in *h and *cpp a file This is the 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 );

Bushey

Why does you .cpp contain the declaration and you .h file the definition of fun(...)? Something seems odd there. – Imitative

i already tried, it is not working – Bushey

This is how I learned: in .cpp the declaration and in .h the definition. It is working in that way for files without ,,vector''. – Bushey

Lots of bugs in code, its not just vector error, solve other bugs vector won't be issue. – Germann

@MIhaela, As soon as two files include the same header, you violate the One Definition Rule. – Pharmacist

"This is how I learned: in .cpp the declaration and in .h the definition" That is backwards. – Glutenous

Answer 1

You've got the declaration in the cpp file and the definition in the header, it should really be the other way round.

After you've swapped the files round remove using namespace std; from functia.h as it's not good practice to pull in namespaces in header files. You'll need to change the declaration to

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

See "using namespace" in c++ headers

I'd also strongly recommend reading C/C++ include file order/best practices

Edvard

Answer 2

Change "vector" to "std::vector"

Neoplasty

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