cpp template class defined in .h files and implemented in cpp files

//MathHelper.h
#ifndef _MathHelper_H
#define _MathHelper_H
#include <iostream>
#include <random>
#include <stdio.h>

using namespace std;

template <class T>
class MathHelper
{
public:
    random_device rd;
    mt19937 mt{rd()};
    T getRandom(T min, T max);
    void getRandomArray(T *arr, T min, T max, int len);
    void printArray(T *arr, int len);
    void randomDemo(T min, T max, int len);
};
#endif



//MathHelper.cpp

#include "Model/MathHelper.h"

template <class T>
T MathHelper<T>::getRandom(T min, T max)
{
    uniform_int_distribution<T> uid(min,max);
    return uid(mt);
}

template <class T>
void MathHelper<T>::getRandomArray(T *arr, T min, T max, int len)
{
    for (int i = 0; i < len; i++)
    {
        T temp=getRandom(min,max);
        arr[i] = temp;
    }
}

template <class T>
void MathHelper<T>::printArray(T *arr, int len)
{
    for (int i = 0; i < len; i++)
    {
        cout << "Index=" << i << ",value=" << arr[i] << endl;
    }
}

template <class T>
void MathHelper<T>::randomDemo(T min, T max, int len)
{
    T *arr = new T[len];
    getRandomArray(arr, min, max, len);
    printArray(arr, len);
    delete[] arr;
    cout << endl
         << "Finished in " << __FUNCTION__ << endl;
}



//main.cpp
#include "Model/MathHelper.h"
#include "Model/MathHelper.cpp"

int main(int args, char **argv)
{
    MathHelper<uint64_t> mh;
    mh.randomDemo(0, UINT64_MAX, atoi(argv[1]));
    cout << "Finished in " << __FUNCTION__ << "," << __LINE__ << endl;
}