constructor - C++ conversion operators -

i know deal .the compiler tries convert 1 object other objects's type of conversion operator .two ways .constructor (converts class other) or conversion operator .so , 1 test if thorough concepts .the code below gives error

using namespace std ; class {     int ;     public:             a(int a=0){this->i=a;}             operator+(const a& b){                     c ;                     return c(this->i+b.i);             }             void show()             {                     cout<<i<<endl;             }  }; int main() {     a1(1),a2(2),a3;     a3=a2+a1;     a3.show();     return 0;  } 

i guess error in operator + .when try assign a(i) .there no match operator create an int .

but see a's constructor lurking behind .it can convert int .suppose , convert int a.then , call becomes a(b) .this equivalent copy constructor .hence , call should work .but doesn't .all in , pretty confused .

please .

in these 2 lines telling compiler construct object default constructor, call nonexistent operator () (int) , return return value:

                c ;                 return c(this->i+b.i); 

use either

a c(i + b.i); return c; 

or

return a(i + b.i); 

on side note, example implicit conversion operator, class:

operator int () const {     return i; } 

but use smells bad design, , can cause bad stuff happen, implicit conversion bool or pointer. use else instead, int toint () const member function.