CODEWITHSUNDEEP
c++11
MistyD
MistyD

Reputation: 17253

Is it possible to return multiple types through a function?

I wanted to know if its possible to return a function that could either return a boolean or a void ? I know I could use std::optional however that is available only in C++17 and my code base is C++11. I would like something like this

xxx process(int a)
{
 if (a==1) 
    return true;
 if (a==2) 
    return false;
 if (a==3)
    .... //return nothing
}

Upvotes: 0

Views: 62

Answers (3)

Sopel
Sopel

Reputation: 1219

If you don't want to write an equivalent of std::optional yourself use an enum.

enum class Result
{
    False,
    True,
    Nothing // or whatever name makes sense in your use case
};

Upvotes: 0

JeanPhi
JeanPhi

Reputation: 127

A variant might be a better match:

According to your requirement: a function that could either return a boolean or a void

See at: http://en.cppreference.com/w/cpp/utility/variant

The class template std::variant represents a type-safe union. An instance of std::variant at any given time either holds a value of one of its alternative types, or it holds no value (this state is hard to achieve, see valueless_by_exception).

Upvotes: 1

Alexcei Shmakov
Alexcei Shmakov

Reputation: 2353

For returning two values I use a std::pair (usually typedef'd). In C++11 and newer, you should use std::tuple for more than two return results.

The abstract example using the tuple

std::tuple<bool, int> process(int a)
{
 if (a==1) 
    return std::make_tuple(true, 0);
 if (a==2) 
    return std::make_tuple(false, 0);
 if (a==3)
    return std::make_tuple(false, 1);
}

Upvotes: 2

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