C++ source code bug -- Computing Differences in Distance and Total Sums - c++

Question

The purpose of this program is to be able to input a set of integer double values, and for it to output the total distance as a sum. It's also meant to recognize the smallest and largest distances -- as well as calculate the mean of two or more distances.
I would also like to be able to remove the repetitive block of code in my program, which I've literally copied to get the second part of the source code working. Apparently there's a way to remove the replication -- but I don't know how.
Here's the source:
/* These includes are all part of a custom header designed
by Bjarne Stroustrup as part of Programming: Principles and Practice
using c++
*/
#include<iostream>
#include<iomanip>
#include<fstream>
#include<sstream>
#include<cmath>
#include<cstdlib>
#include<string>
#include<list>
#include <forward_list>
#include<vector>
#include<unordered_map>
#include<algorithm>
#include <array>
#include <regex>
#include<random>
#include<stdexcept>
// I am also using the "stdafx.h" header.
// reading a sequence of integer doubles into a vector.
This could be the distance between two areas with different paths
int main()
{
vector<double> dist; // vector, double integer value
double sum = 0; // sum of two doubles
double min = 0; // min dist
double max = 0; // max dist
cout << "Please enter a sequence of integer doubles (representing distances): \n";
double val = 0;
while (cin >> val)
{
if (val <= 0)
{
if (dist.size() == 0)
error("no distances");
cout << "The total distance is: " << sum << "\n";
cout << "The smallest distance is: " << min << "\n";
cout << "The greatest distance is: " << max << "\n";
cout << "The average (mean) distance is: " << sum / dist.size() << "\n";
keep_window_open();
return 0;
}
dist.push_back(val); // stores vector value
// updating the runtime values
sum += val;
if (val > min)
min = val;
if (max < val)
max = val;
}
if (dist.size() == 0)
error("no distances");
cout << "The total distance is: " << sum << "\n";
cout << "The smallest distance is: " << min << "\n";
cout << "The greatest distance is: " << max << "\n";
cout << "The average (mean) distance is: " << sum / dist.size() << "\n";
keep_window_open();
}
Additionally, I have been trying to input a small block of source code in the form of something like "catch (runtime_error e)" but it expects a declaration of some sort and I don't know how to get it to compile without errors.
Help with removing the replicated/repeating block of code to reduce bloat would be great -- on top of everything else.

Answer 1

Instead of having the if statement inside the while, you should combine the two conditions to avoid duplicating that code:
while ( (cin >> val) && (val > 0) )
Also, you need to initialize min to a largest value, rather than zero, if you want the first comparison to capture the first possible value for min.
Making a function out of duplicated code is a general purpose solution that isn't a good choice in your case for two reasons: First, it isn't necessary, since it is easier and better to combine the flow of control so there is no need to invoke that code in two places. Second there are too many local variables used in the duplicated code, so if there were a reason to make the duplicated code into a function, good design would also demand collecting some or all of those local variables into an object.
If it had not been cleaner and easier to merge the two conditions, it still would be better to merge the flow of control than to invent the function to call from two places. You cold have used:
if (val <= 0)
{
break;
}