CODEWITHSUNDEEP
c++functionstructreturn
Arun Kumar
Arun Kumar

Reputation: 17

What is the appropriate manner to return a struct from a called function to a calling function in C++?

I have a function which takes in two int values, does some processing and then returns the processed values in the form of a struct to the calling function.

The following is my called function:

auto start_end(){
bool cond = false;
int xd = 0;
int yd = 0;
std::cout<<("Please enter a desired x coordinate")<<std::endl;

std::cin>>xd;
while(std::cin.fail()){
   std::cout<<("That is not a valid integer. Please enter a valid x co-ordinate")<<std::endl;
   std::cin.clear();
   std::cin.ignore(256,'\n');
   std::cin>>xd;
   }
   std::cout<<("Please enter a desired y coordinate")<<std::endl;

std::cin>>yd;
while(std::cin.fail()){
   std::cout<<("That is not a valid integer. Please enter a valid y co-ordinate")<<std::endl;
   std::cin.clear();
   std::cin.ignore(256,'\n');
   std::cin>>yd;
   }
struct xy{int x_received; int y_received;};
return xy{xd,yd};
}

We can see that the struct xy returns two values xd, yd in the above function start_end().

The following is my calling function:

int main(int argc, const char * argv[]) {
std::cout <<("A-Star-Algorithm for Project 2 obstacle map")<<std::endl;
int x_start = 0;
int y_start = 0;
int init_point = start_end();


return 0;
}

So when I try to store the return values xd, yd in the variable init_point, I get the error: 

No viable conversion from 'xy' to 'int'

Since, I got this error I tried to write the receiving variable as a 2 - index array:

int init_point[2] = start_end();

When I try to do in this way, I get the following error:

 Array initializer must be an initializer list

My exact question : What is the appropriate manner in which I have to receive the values xd and yd returned by function start_end() when it is called inside function int main() ?

Upvotes: 0

Views: 68

Answers (2)

Lingxi
Lingxi

Reputation: 14987

std::tuple is to your relief (live)

#include <iostream>
#include <tuple>

auto start_end() {
  auto x = 1, y = 2;
  return std::make_tuple(x, y);
}

int main() {
  int x, y;
  std::tie(x, y) = start_end();
  std::cout << x << ' ' << y << std::endl;
}

Upvotes: 2

Tas
Tas

Reputation: 7111

You need to move your struct into a place that can be seen by start_end and main:

struct xy { int x; int y; };
xy start_end()
{
    ...
    return { xd, yd };
}
int main()
{
}

Then you can either assign it with auto or use the type name xy:

int main()
{
    auto xy1 = start_end();
    xy xy2 = start_end();
}

Or you can use std::pair or std::tuple.

Upvotes: 4

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