My bad - I am not a C programmer. Here is a corrected version that follows the convention of writing proper C:

```
#include<stdio.h>
#include<math.h>

double AttackerSuccessProbability(double q, int z)
{
 double p = 1.0 - q;
 double lambda = z * (q / p);
 double sum = 1.0;
 int i, k;
 for (k = 0; k <= z; k++)
 {
 double poisson = exp(-lambda);
 for (i = 1; i <= k; i++)
 poisson *= lambda / i;
 sum -= poisson * (1 - pow(q / p, z - k));
 }
 return sum;
}

int main() {
  //If the attacker is one block behind and there is 49% of dishones nodes
  double prob = AttackerSuccessProbability(0.49, 1);
  puts("The probability of the success of the attacker when they are 1 block behind the honest 51% majority of nodes:");
  printf("%f\n", prob);
  
return 0;	
}

```

The first version works just as well, but is not as elegant.

denationalized

bitcoin_beginners

Taking a closer look at Satoshi's calculations written in C

You have a small error as the function is defined inside the main().

Anyway, here is an online version that anyone can run from the web: https://glot.io/snippets/gu79r84jce

![a.png](https://m.stacker.news/20050)