C++: handling errors, can't understand my mistake [closed] - c++

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1.Check the user input. If the input does not match three floating-point numbers, output an error message and do not start the calculation.
2.Check whether a==0. If so, throw a runtime_error and catch it in main, printing a message saying that a must not be 0.
The error messages should look like this:
An error occured: Malformed user input
An error occurred: a must not be zero
#include <iostream>
#include <cmath>
#include <vector>
#include <stdexcept>
using namespace std;
vector<double> solutionFinal (double a, double b, double c){
double s1, s2, discriminant;
discriminant = b*b - 4*a*c;
if (discriminant > 0){
s1 = (-b + sqrt(discriminant)) / (2*a);
s2 = (-b - sqrt(discriminant)) / (2*a);
cout << "There are 2 solutions." << endl;
cout << "The solutions are: " << s1 << " and " << s2;
return {s1, s2};
}
else if (discriminant == 0) {
cout << "There is 1 solution." << endl;
s1 = (-b + sqrt(discriminant)) / (2*a);
cout << "The solution is: " << s1;
return {s1};
}
else {
cout << "There is no solution." << endl;
return {};
}
}
int main (){
double a, b, c;
cout << "Please enter the values of a, b, and c respectively:" << endl;
try{
if (!(cin >> a >> b >> c)) {
throw runtime_error("An error occured: Malformed user input");
}
if (a == 0) {
throw runtime_error("An erorr occured: a must not be zero");
}
}
auto result = solutionFinal(a, b, c);
for (auto scalar : result){
}
catch (runtime_error& excpt) {
cout << excpt.what();
}
return 0;
}

Answer 1

Your code is malformed, your braces don't add up. I prefer another brace style because I think it's easier to see that way:
#include <iostream>
#include <cmath>
#include <vector>
#include <stdexcept>
using namespace std;
vector<double> solutionFinal (double a, double b, double c)
{
double s1, s2, discriminant;
discriminant = b*b - 4*a*c;
if (discriminant > 0)
{
s1 = (-b + sqrt(discriminant)) / (2*a);
s2 = (-b - sqrt(discriminant)) / (2*a);
cout << "There are 2 solutions." << endl;
cout << "The solutions are: " << s1 << " and " << s2;
return {s1, s2};
}
else if (discriminant == 0)
{
cout << "There is 1 solution." << endl;
s1 = (-b + sqrt(discriminant)) / (2*a);
cout << "The solution is: " << s1;
return {s1};
}
else
{
cout << "There is no solution." << endl;
return {};
}
}
int main ()
{
double a, b, c;
cout << "Please enter the values of a, b, and c respectively:" << endl;
try
{
if (!(cin >> a >> b >> c))
{
throw runtime_error("An error occured: Malformed user input");
}
if (a == 0)
{
throw runtime_error("An erorr occured: a must not be zero");
}
// this block was outside the try, between the try and the catch.
// it MUST be inside the try block like this
auto result = solutionFinal(a, b, c);
for (auto scalar : result)
{
}
}
catch (runtime_error& excpt)
{
cout << excpt.what();
}
return 0;
}