GeeksforGeeks » C/C++ Programming Questions

Output of C++ program?

(2 posts)

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  1. Brill
    guest
    Posted 1 year ago # 

    #include<iostream>
int f() {
    return 2;
}

class temp
{
  public:
  int operator()() {
    return 1;
  }
};

int main()
{
  temp f;
  std::cout<<f();
  getchar();
  return 0;
}

  2. Venki
    Moderator
    Posted 1 year ago #

    Answer 1.

    It is due to the overloading "conversion function" 'operator()()'. Conversion functions (functor) are useful for passing parameters and returning appropriate type.

    Another form is 'conversion operator'

    syntax ----- operator type-name () {}

    Conversion operator converts the user defined concrete type into required type. Example,

    class RollCommand
    {
    public:
    // Some processing functions

    operator const double ()
    {
    return rollAngle;
    }
    private:
    double rollAngle;
    };

    RollCommand rc;
    ...
    // Backs up the previous roll angle
    backUp = rc;

    The return type need not necessarily the primitive type. It can be another user defined type. The functor will do necessary conversions prior to returning the intended object.


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