CODEWITHSUNDEEP
c++functionfile
Artur
Artur

Reputation: 25

Wrong values after returning from function c++

My function reads data from file and it works well, but when I return data something goes wrong. This is how it looks like:

Console

Code:

struct csvh
{
//struct declaration
};


float glowa_csv(csvh CSVHead, float EndOfHead)
{
    ifstream obraz;
    obraz.open("POP_OCT.csv", ios::binary);
    //wczytywanie naglowka
    obraz.read(CSVHead.data, sizeof(CSVHead.data)-1); 
    obraz >> CSVHead.lateral_range;
    obraz.read(CSVHead.lat_px_size, sizeof(CSVHead.lat_px_size)-1);
    obraz >> CSVHead.lateral_pxsize;
    ... ( and so on)

    EndOfHead=obraz.tellg();
    obraz.close();

    cout << CSVHead.data<<endl<<CSVHead.godzina<<(rest of variables)<<endl;

    return CSVHead.lateral_range, CSVHead.lateral_pxsize, (...), EndOfHead;
} 

int main()
{
    float EndOfHead;
    csvh CSVHead;

    glowa_csv(CSVHead, EndOfHead);

    system("Pause");
    system("cls");
    cout << CSVHead.data<<endl<<CSVHead.godzina<<(...)<<endl;
    return 0;
}

Upvotes: 1

Views: 95

Answers (2)

ChrisF
ChrisF

Reputation: 137158

If you want to return multiple values from a function you must either return a class/struct or pass the variables by reference.

Passing by reference is perfectly valid but can be confusing for some people, so returning a complex object might be the "better" solution. You can return values in Tuple:

std::tuple<int,int,int> method(int input)
{
  /* do your stuff here */

  return { errorCode , value1 , value2 };
}

so you don't have to create extra types. Obviously the exact types in the tuple will depend on what you need to return

Upvotes: 4

NathanOliver
NathanOliver

Reputation: 180935

First off you cannot return multiple values from a function like

return CSVHead.lateral_range, CSVHead.lateral_pxsize, (...), EndOfHead;

This winds up only returning EndOfHead thanks to the comma operator. What it looks like you want to do is pass CSVHead and EndofHead by reference so that the function modifies the variables you pass to it and the changes are reflected in main(). You can change the function to

void glowa_csv(csvh &CSVHead, float &EndOfHead)

And get rid of the return statement entierly.

Upvotes: 3

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