HELP!

Need help in correcting these codes.  Below are 4 independant files with the generated output to each.  Please help in providing corrected actual codes.  Thank you.

// ver5.cpp
#include <iostream>
#include <cmath>

using namespace std;

void input fun(p_array);
double calculate fun(p_array);

int main() {


   double p_array[2][3]; // data structure, memory location for your variable
   double d;

   input fun(p_array);
   calculate fun(p_array);
   print fun(double d);

   d = calculation function;

   print fun(d);

   return 0;

}

ver5.cc:6: `p_array' was not declared in this scope
ver5.cc:6: variable or field `inputFun' declared void
ver5.cc:7: `p_array' was not declared in this scope
ver5.cc: In function `int main()':
ver5.cc:15: variable or field `inputFun' declared void
ver5.cc:15: initialization to `int' from `double (*)[3]' lacks a cast
ver5.cc:16: initialization to `double' from `double (*)[3]'
ver5.cc:17: parse error before `)'
ver5.cc:19: `calculation' undeclared (first use this function)
ver5.cc:19: (Each undeclared identifier is reported only once
ver5.cc:19: for each function it appears in.)
ver5.cc:19: parse error before `;'
ver5.cc:21: `print' undeclared (first use this function)

// ver_6.cpp
#include <iostream>

using namespace std;

void input_fun(double p_array[2][3]);
double calculate_fun(double p_array[2][3]);
void print_fun(double distance);

int main() {

   double p_array[2][3];
   double distance;

   input_fun(p_array);
   distance = calculate_fun(p_array);
   print_fun(distance);

   return 0;

}

void input_fun(double p_array[2][3]) {

   for(int i = 0; i <= 1; i++)
       for(int j = 0; j <= 2)
            cin >> p_array[i][j];

}

double calculate_fun(double p_array[2][3]) {

   double distance;
     
   distance =

   return distance;

}

void print_fun(double distance) {

   cout << "distance = " << distance << endl;

}

ver_6.cpp: In function `void input_fun(double (*)[3])':
ver_6.cpp:27: parse error before `)'
ver_6.cpp:38: parse error before `return'
ver_6.cpp:42: parse error before `{'

// ver_7.cpp
#include <iostream>

using namespace std;

int main()
{
   point p_array[2];
   double distance;
   inputFun(p_array);
   distance = calculate_fun(p_array);
   printFun(distance);

   return 0;

}

ver_7.cpp: In function `int main()':
ver_7.cpp:9: `point' undeclared (first use this function)
ver_7.cpp:9: (Each undeclared identifier is reported only once
ver_7.cpp:9: for each function it appears in.)
ver_7.cpp:9: parse error before `['
ver_7.cpp:11: `p_array' undeclared (first use this function)
ver_7.cpp:11: implicit declaration of function `int inputFun(...)'
ver_7.cpp:12: implicit declaration of function `int calculate_fun(...)'
ver_7.cpp:13: implicit declaration of function `int printFun(...)'

// ver_8.cpp
#include <iostream>

using namespace std;

int main()
{
   DistanceOfPoints obj_1;
   obj_1.inputFun();
   obj_1.calculateFun();
   obj_1.printFun();

   return 0;

}

ver_8.cpp: In function `int main()':
ver_8.cpp:7: `DistanceOfPoints' undeclared (first use this function)
ver_8.cpp:7: (Each undeclared identifier is reported only once
ver_8.cpp:7: for each function it appears in.)
ver_8.cpp:7: parse error before `;'
ver_8.cpp:8: `obj_1' undeclared (first use this function)