How do I terminate an "auto" type function with a structure return type during execution?
I want to escape the auto function 'Func' (not the entire program) when some condition is satisfied as follows:
#include "stdafx.h"
#include <vector>
#include <tchar.h>
#include <iostream>
using namespace std;
auto Func(int B, vector<int> A) {
for (int a = 0; a < B; a++)
{
A.push_back(a);
if (a == 2)
{
cout << " Terminate Func! " << endl;
// return; I want to terminate 'Func' at this point
}
}
struct result { vector <int> A; int B; };
return result{ A, B };
}
int _tmain(int argc, _TCHAR* argv[])
{
vector<int> A;
int B = 5;
auto result = Func(B, A);
A = result.A;
B = result.B;
for (int a = 0; a < A.size(); a++)
{
cout << A[a] << endl;
}
}
I don't want to use "exit()" because I just want to terminate a function not the program.
The exit() is a function and not a command. Unlike the return statement, it will cause a program to stop execution even in a function. And the exit() function can also return a value when executed, like the return statement. So the C family has three ways to end the program: exit(), return, and final closing brace.
We know we can break out of loops using the built-in break function in C++. Similarly, we can also break out of a whole C++ program using the exit() function.
The exit () function is used to break out of a loop. This function causes an immediate termination of the entire program done by the operation system. The general form of the exit() function is as follows − void exit (int code);
return is a statement that returns the control of the flow of execution to the function which is calling. Exit statement terminates the program at the point it is used.
You can return a define the return type result
at the top of the function and then return an "empty" instance like this:
auto Func(int B, vector<int> A) {
struct result { vector <int> A; int B; };
for (int a = 0; a < B; a++)
{
A.push_back(a);
if (a == 2)
{
return result{{}, 0};
}
}
return result{ A, B };
}
If you don't want a valid object to be returned when the early-return condition is met, consider returning a std::optional<result>
from the function, and specifically std::nullopt
in the early return branch. But this requires C++17.
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