Get more than one value out of an function

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Returning multiple values from a C++ function

/************************************************/
/* Name: premserv                               */
/* Description: Calculations for premium serv   */
/* Parameters: N/A                              */
/* Return Value: premserv                       */
/************************************************/

float premserv ()
{
  int daymin = 0;         //Var for day minutes
  int nightmin = 0;       //Var for night minutes
  float daytotal = 0;     //Var for day total
  float nighttotal = 0;   //Var for night total
  float premserv = 0;     //Var for premium service cost

  cout << "\n" << "Please enter the number of minutes used durring the day (6AM - 6PM): " << "\n";
  cin >> daymin;
  cout << "\n" << "Please enter the number of minutes used durring the night (6PM - 6AM): " << "\n";
  cin >> nightmin;

  daytotal = (daymin - 75) * 0.1;
  nighttotal = (nightmin - 100) * 0.05;
  premserv = 25 + daytotal + nighttotal;

  return premserv;

}

I need to get the values from daymin, nightmin, and premserv out of the function. I only know how to get 1 value out of a function.

Please don't start every question title with the word "c++". That's already in the tags. Thanks. — Lightness Races in Orbit, Oct 19 '11 at 21:41

score 8 · Answer 1 · answered Oct 19 '11 at 21:31

8

Create a struct with all three floats and return that instead of the single float.

answered Oct 19 '11 at 21:31

plackemacher

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score 3 · Accepted Answer · edited Oct 19 '11 at 21:40

3

You could use references.

float premserv (int& daymin, int& nightmin)
{
     float daytotal = 0;     //Var for day total
     float nighttotal = 0;   //Var for night total
     float premserv = 0;     //Var for premium service cost

     cout << "\n" << "Please enter the number of minutes used durring the day (6AM - 6PM): " << "\n";
     cin >> daymin;
     cout << "\n" << "Please enter the number of minutes used durring the night (6PM - 6AM): " << "\n";
     cin >> nightmin;

     daytotal = (daymin - 75) * 0.1;
     nighttotal = (nightmin - 100) * 0.05;
     premserv = 25 + daytotal + nighttotal;

     return premserv;
}

This will directly modify the values of daymin and nightmin and you could still keep premserv as a returned value (since it fits with the function name, I guess).

You'd use it like so:

int daymin = 0;
int nightmin = 0;
float premiumservice = premserv(daymin, nightmin);

edited Oct 19 '11 at 21:40

Lightness Races in Orbit

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answered Oct 19 '11 at 21:31

Jesse Emond

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do i need to declare those variables in int main then? – Sam LaManna Oct 19 '11 at 21:32
@SamLaManna: Yes, they have to exist so you can pass a **reference** to them. – ereOn Oct 19 '11 at 21:33
(I wouldn't usually make such a subjective edit, but I feel quite strongly that [this one is important for language newcomers](http://kera.name/articles/2010/05/tomalaks-monday-monstrous-rant-i-align-your-asterisks/) like the OP.) – Lightness Races in Orbit Oct 19 '11 at 21:34
Variable names the same as function names? Hmm... >. – Lightness Races in Orbit Oct 19 '11 at 21:35
its just the return and i always assign it to a different var name in int main. premserv becomes premiumservice – Sam LaManna Oct 19 '11 at 21:38
@TomalakGeret'kal: Interesting, I always used my method and thought it was just okay. I'll edit my post. (As for the variable name, yeah, sorry I did it a little quickly without thinking) – Jesse Emond Oct 19 '11 at 21:38
So were do i use the & and were dont I – Sam LaManna Oct 19 '11 at 21:40
@Jesse: Why do you keep reverting my edit if you're okay with it? – Lightness Races in Orbit Oct 19 '11 at 21:40
I get error: expected primary-expression before "int" and declaration of int daymin and int nightmin shadows a parameter – Sam LaManna Oct 19 '11 at 21:44
@TomalakGeret'kal: Oh really? Oh. My bad. I just moved the `&` without really thinking, telling myself that I had to move it to the opposite of what it was. I did not notice your edit. Thank you, though. – Jesse Emond Oct 19 '11 at 21:45
@Sam: Then you're not using the code that Jesse showed you. – Lightness Races in Orbit Oct 19 '11 at 21:46
Here is the whole thing, with all changes made: [link]http://pastebin.com/NnrxnVHU – Sam LaManna Oct 19 '11 at 21:48
@SamLaManna: Remove the `int`s when calling the function. You are passing the variable name, not its type. That's how the syntax of references works. :) – Jesse Emond Oct 19 '11 at 21:51
Thanks but i still have an error: 'declaration of 'int daymin' shadows a parameter'. The same thing for nightmin – Sam LaManna Oct 19 '11 at 21:53
@SamLaManna: remove the declarations of `daymin` and `nightmin` within the function. You're passing the references, so you don't need to redeclare them once again, since you just pass them to the function. i.e. get rid of those lines: int daymin = 0; //Var for day minutes int nightmin = 0; //Var for night minutes – Jesse Emond Oct 19 '11 at 21:58

score 1 · Answer 3 · answered Oct 19 '11 at 21:32

1

in c, create a structure to hold above said 3 values. in c++ create a class and return an object of the class.

answered Oct 19 '11 at 21:32

Ravi Bhatt

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You said the same thing twice. – Lightness Races in Orbit Oct 19 '11 at 21:37

score 1 · Answer 4 · answered Oct 19 '11 at 21:33

float premserv(int& daymin, int& nightmin) { 
    float daytotal = 0;     //Var for day total    
    float nighttotal = 0;   //Var for night total    
    float premserv = 0;     //Var for premium service cost    
    // etc...

'premserv' is already being returned.

bames53 · Answer 5 · 2013-11-05T22:00:06.430

Another option besides using out parameters or defining a specific struct return type is to use tuples from C++11 or TR1:

/* Return Value: tuple<daymin,nightmin,premserv>   */
/***************************************************/

std::tuple<int,int,float> premserv ()
{
  // ...
  return std::make_tuple(daymin, nightmin, premiumservice);
}

Then you can use it like this:

int daymin, nightmin;
float premiumservice;
std::tie(daymin,nightmin,premiumservice) = premserv();

Or if you just care about one of the values:

int nightmin = std::get<1>(premserv());

zar · Answer 6 · 2011-10-19T21:43:54.613

0

You got multipel answers but alternatively you can return struct in the function parameter so you have one object to deal with and return value will tell you if the data is valid or not.

struct
{
   float premserv;
   int daymin;
   int nightmin;

} data;

bool premserv (data & my_data)
{
   // ...
}

if( premserv(my_data) == true )
{
  // user the data
}

edited Oct 19 '11 at 21:43

answered Oct 19 '11 at 21:38

zar

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Get more than one value out of an function

6 Answers6