Int64 in some Gaussian Randomness Code

Question

So I'm reading an AI book and it is talking about Gaussian Randomness and it includes this example code

unsigned long seed = 61829450;
double GaussianRand()
{
  double sum = 0;
  for (int i = 0: i < 3; i++)
    {
       unsigned long holdseed = seed;
       seed^= seed << 13;
       seed^= seed >> 17;
       seed^= seed << 5;
       long r = (Int64)(holdseed + seed);
       sum += (double)r * (1.0/0x7FFFFFFFFFFFFFFF);
    }
  return sum; //returns [-3.0, 3.0] at (66.7%, 95.8%, 100%)

So taking some of the knowledge I have learned from using C++ here at my University, I did this with it.

#include <iostream>
#include <random>
#include <inttypes.h>

using namespace std;

double GaussianRand();

int main()
{
  GaussianRand();
}

double GaussianRand()
{
  double sum = 0;
  for (int i = 0; i < 3; i++)
    {
      unsigned long holdseed = seed;
      seed^= seed << 13;
      seed^= seed >> 17;
      seed^= seed << 5;
      long r = (Int64)(holdseed + seed);
      sum += (double)r * (1.0/0x7FFFFFFFFFFFFFFF);
    }
  return sum;
}

I am running into the problem of not understanding what Int64 is or how I am supposed to be using it. I have googled some things and I think I am just confusing myself on this since I have not actually seen this before or learned it. Is int64_t the same thing as Int64 or are they two completely different thing?

------------------THIS IS AN UPDATE I PROMISED YESTERDAY------------------------

So after a bit of playing around I found out that to use Int64 I have to use the

using namespace System;

line of code. To do this I had to create a project that was a CLR Console Application and just stick the code in there. The code looks like this now

#include "stdafx.h"
#include <iostream>
#include <random>

using namespace System;
using namespace std;

unsigned long seed = 61829450;
double GaussianRand();

int main()
{
 GaussianRand();
}

double GaussianRand()
{
 double sum = 0;
 for (int i = 0; i < 3; i++)
 {
  unsigned long holdseed = seed;
  seed ^= seed << 13;
  seed ^= seed >> 17;
  seed ^= seed << 5;
  long r = (Int64)(holdseed + seed);
  sum += (double)r * (1.0 / 0x7FFFFFFFFFFFFFFF);
  cout << sum << endl;
 }
 cout << sum << endl;
 return sum;  /// returns [-3.0, 3.0] at [67.7%, 95.8%, 100%]
}

It compiles and runs without any problems.

Thank you to everyone who helped me figure this out

Answer 1

Int64 is not a standard C++. It's not hard to see that there is no workaround which makes int == int32_t == long on 32-bit systems. For the same reason, there's no way to make long == int64_t == long long on 64-bit systems.

Add this include to your project:

#include <inttypes.h>

Then use uint64_t or int64_t.

what is the difference between <stdint.h> and <inttypes.h>?

<inttypes.h> includes <stdint.h> and just adds more macros/functions. So both should be fine.