Generic Class Data member calling Functions.

[SaadBukhari66]

using namespace std;

template <class HASH, class intT>
class Table {
 private:
  typedef typename HASH::eType eType;
  typedef typename HASH::kType kType;
  intT m;
  intT mask;
  eType empty;
  HASH hashStruct;
  eType* TA;
  intT* compactL;

This is simple definition of the class ( only some part of it), the problem is that data member defined above HASH hashStruct has called some functions where as it is a generic data member only, for example within a class it is used to call a function like

intT firstIndex(kType v) {

return hashToRange(hashStruct.hash(v));
}

Here hashStruct has called a function within the class Table , but the function called are described in the three structures which are given below( which are defined outside the definition of class)

3 different places below in the code are the structures containing the functions which are called by hashStruct, which are as follows:

1:

template <class intT>
struct hashInt {
  typedef intT eType;
  typedef intT kType;
  eType empty() {return -1;}
  kType getKey(eType v) {return v;}
  uintT hash(kType v) {return utils::hash(v);}
  int cmp(kType v, kType b) {return (v > b) ? 1 : ((v == b) ? 0 : -1);}
  bool replaceQ(eType v, eType b) {return 0;}
};

2:

struct hashStr {
  typedef char* eType;
  typedef char* kType;

  eType empty() {return NULL;}
  kType getKey(eType v) {return v;}

  uintT hash(kType s) {
    uintT hash = 0;
    while (*s) hash = *s++ + (hash << 6) + (hash << 16) - hash;
    return hash;
  }

  int cmp(kType s, kType s2) {
    while (*s && *s==*s2) {s++; s2++;};
    return (*s > *s2) ? 1 : ((*s == *s2) ? 0 : -1);
  }
  bool replaceQ(eType s, eType s2) {return 0;}
};

3:

template <class KEYHASH, class DTYPE>
struct hashPair {
  KEYHASH keyHash;
  typedef typename KEYHASH::kType kType;
  typedef pair<kType,DTYPE>* eType;
  eType empty() {return NULL;}

  hashPair(KEYHASH _k) : keyHash(_k) {}

  kType getKey(eType v) { return v->first; }

  uintT hash(kType s) { return keyHash.hash(s);}
  int cmp(kType s, kType s2) { return keyHash.cmp(s, s2);}

  bool replaceQ(eType s, eType s2) {
    return s->second > s2->second;}
};

These all functions are called at different places by hashStruct in the code, I have highlighted only one in the start.
I want to know some sound explanation how it is able to call functions, the logic behind it , the all code is placed in the header file. Because as far as I know the objects of class can call functions through "." operator How can generic data member.