Problem with calling member functions of a struct in MQL4.

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Hi, I have a problem with calling member functions. They seem to be called as regular functions and do not modify struct member variables. The reason for this could be my "vector" array wrapper.
```
template < typename T >
struct vector {
  vector() {}
  vector(int arraySize) {
     if (arraySize < 0) { arraySize *= -1; }
     ArrayResize(m_data, arraySize);
  }
  vector(vector & rhs) {
     if (size() < rhs.size()) { ArrayResize(m_data, rhs.size()); }
     for(uint i = 0; i < size(); ++i) { m_data[i] = rhs.m_data[i]; }
  }
  vector operator=(vector & rhs) {
     if (size() < rhs.size()) { ArrayResize(m_data, rhs.size()); }
     for(uint i = 0; i < size(); ++i) { m_data[i] = rhs.m_data[i]; }
     return this;
  }
  T operator[](uint index) { return m_data[index]; }
  void push_back( T & value ) {
     ArrayResize(m_data, ArraySize(m_data) + 1);
     m_data[ ArraySize(m_data) - 1 ] = value;
  }
  uint size() { return ArraySize(m_data); }
  void resize(uint newSize) { ArrayResize(m_data, newSize); }
  void erase() {
     ZeroMemory(m_data);
     ArrayResize(m_data, 0);
  }
  void assign(uint index, T & value) {
     m_data[index] = value;
  }
  T last() { return m_data[ ArraySize(m_data) - 1 ]; }
private:
  T m_data[];
};

//program

struct Something {
   Something() : x(0.0), y(0.0) {}
  
   void Make(double a, double b) { x = a; y = b; }
   double Get() { return x+y; }
  
   double x,y;
};

vector<Something> things;

void OnStart()
{
   for(int i = 0; i < 10; ++i) {
      things.push_back( Something() );
   }
  
   for(uint i = 0; i < things.size(); ++i) {
      things[i].Make(i, i*i);
   }
  
   string s;
   for(uint i = 0; i < things.size(); ++i) {
      s += (string)things[i].Get() + "\n";
   }
  
   Alert ( s );
}
```

This script is printing 0 for each element instead of i+i*i sum.
 
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  2. things[i].Make(i, i*i);
    This doesn't do what you think it does.  
    T operator[](uint index) { return m_data[index]; }
    Operator[] makes a copy and returns it. You then update the copy and then throw it away. You would know this had you simply stepped into the code with the debugger.
  3. You can't return a pointer, because it's a struct not a class.
  4. If it was a class and you returned a pointer, then the Make would be updating the original.
 
Thank you. I didn't know the difference between struct and class in MQL4. I thought pointers are not available in MQL.
 
Mikołaj Gogola:  I thought pointers are not available in MQL.

Correct, only handles to a class. They act like references. A lot has changed since Build 600 and Higher. 2014.02.03

 
Is any graceful way to make my vector class work on basic types like double or int?
I could do wrapper class around basic types
class Double {
public:
   double value;
};
but there is still need to get underlying basic type with dot operator 
vector <Double> myVector;
myVector[4].value = 7.5;
and I can't create macro to hide it, because macro has to have the same name as the struct and it is not allowed.
How can I make it work?
 
Mikołaj Gogola: Is any graceful way to make my vector class work on basic types like double or int?

No, because MTx doesn't have pointers. Your operator[] can't return a pointer, so you can not write v[i]=v.

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