error C2065: 'NULL' : undeclared identifier
You haven't included <cstddef>
, which defines NULL
.
error C2065: 'value' : undeclared identifier
You forgot to include the class name when you defined the member functions, so instead declared new non-member functions:
int Singelton::get_value()
{// ^^^^^^^^^^^
return value;
}
You should also spell "singleton" properly and avoid reserved names like __SINGELTON_H__
. Hopefully, you'll soon be taught why singletons are a bad idea in general, and doubly so in C++. Have a look here, in case your teacher forgets to cover that.