CODEWITHSUNDEEP
c++
user5494873
user5494873

Reputation:

How to declare a function in a header that takes a pointer as an argument?

I have solved quite a few of Euler problems by now and have been thinking of a more clever way to reuse my functions I have written for earlier problems. So I thought of making a header file that will contain all my useful functions. So far I have been able to successfully include this in my header file without any errors.

#include <cmath>
bool isPrime(long int n)
{
  if( n<=0 ) return false; 
  if( n==1 ) return false;
  else if( n < 4 ) return true;
  else if( n%2 == 0 ) return false;
  else if( n<9 ) return true;
  else if( n%3 == 0 ) return false;

  else{ 
    int r = floor(sqrt(n)); 
    int f = 5;
    while( f <= r ){ 
      if(n%f == 0) return false;
      if(n%(f+2) == 0) return false;
      f += 6; 
    }

    return true;
  }
}

Now I would like to add to in a function that prints out the contents of a vector that can hold any type of variables, so I thought of doing something like this in my header file,

#include <iostream>
#include <vector>

template <typename T>
T printVec(vector<T>* a){
  for(int i=0; i<a->size(); i++)
    cout << a->at(i) << ", ";
  cout << endl;
}

This however has a few issues, is doesn't like the template and it complains about a not being declared?

Could you please let me know on how to get this done?

Thank you

Upvotes: 1

Views: 159

Answers (2)

Prophet Daniel
Prophet Daniel

Reputation: 327

Just make sure you are utilizing namespace std by adding namespace std; just after includes. If utilizing C++11, this solves your problem:

#include <iostream>
#include <vector>

using namespace std;

template <typename T>
void printVec(vector<T> a){
  for(auto vectorElement: a)
    cout << vectorElement << ", ";
  cout << endl;
}

int main(void){
    vector<int> aVec = {1,2,3,4};
    printVec(aVec);
}

Try this cpp.sh/8llel just for reference. Keep in mind your printVec doesn't return a thing so it should be declared void.

Upvotes: 0

Jarod42
Jarod42

Reputation: 218098

std:: are missing:

There are also improvement, const reference is better than pointer

template <typename T>
void printVec(const std::vector<T>& a) {
  for (std::size_t i = 0; i != a.size(); ++i) {
    std::cout << a.at(i) << ", ";
  }
  std::cout << std::endl;
}

or even (in C++11)

template <typename T>
void printVec(const std::vector<T>& a){
  for (const auto& e : a) {
    std::cout << e << ", ";
  }
  std::cout << std::endl;
}

or

void printVec(const std::vector<T>& a){
    std::copy(a.begin(), a.end(), std::ostream_iterator<T>(std::cout, ", "));
    std::cout << std::endl;
}

Upvotes: 1

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