list< TTreeObj<DataT>* >::iterator iterator_begin=childs->begin();

"ap_common.h", line 851: error: expected a ";"

template <typename DataT> class TTreeObj
{
private:
    TTreeObj<DataT>* parent;
    list<TTreeObj<DataT>*> *childs;
public:
    TTreeObj(DataT d=0, TTreeObj<DataT>* p=NULL) : info(d), parent(p), childs(NULL) {}
    DataT info;
.....
};
typedef TTreeObj<DataT> TreeObjRefT;

template <typename DataT> TTreeObj<DataT>* TTreeObj<DataT>::operator[](int Index)
{
......
    list<TreeObjRefT*>::iterator iterator_begin=childs->begin();
.....
    return *iterator_begin;
}

"ap_common.h", line 817: error: identifier "DataT" is undefined

template <typename DataT> class TTreeObj
{
private:
    TTreeObj<DataT>* parent;
    list<TTreeObj<DataT>*> *childs;
public:
    TTreeObj(DataT d=0, TTreeObj<DataT>* p=NULL) : info(d), parent(p), childs(NULL) {}
    DataT info;
.....
typedef TTreeObj<DataT> TreeObjRefT;
};

template <typename DataT> TTreeObj<DataT>* TTreeObj<DataT>::operator[](int Index)
{
......
    list<TreeObjRefT*>::iterator iterator_begin=childs->begin();
.....
    return *iterator_begin;
}

"ap_common.h", line 827: error: identifier "iterator_begin" is undefined