Collection.h

#ifndef COLLECTION_H
#define COLLECTION_H

// Preliminary

class CollectionI { 
public:
    // A primitive integer type that is wide enough to be both pointer to 
    // elem and index.
    #ifdef ILP32
    typedef int ci_index_t;
    typedef int ci_value_t;
    #elif LP64
    typedef long ci_index_t;
    typedef long ci_value_t;
    #elif LLP64
    typedef long long ci_index_t;
    typedef long long ci_value_t;
    #endif 
    
    // The NULL or 'invalid' index (iteration starts and stops here)
    virtual ci_index_t docall GetNullIndex( ) = 0;
    virtual ci_index_t docall GetNullValue( ) = 0;
    
    // Step fwd / bwd
    virtual ci_index_t docall Next( ci_index_t prv ) = 0;
    virtual ci_index_t docall Prev( ci_index_t prv ) = 0;
    
    // Get/Set
    virtual ci_value_t docall Get( ci_index_t ix ) = 0;
    virtual bool docall Set( ci_index_t ix, ci_value_t val ) = 0;
    
    // Type of elements
    virtual int docall GetElemType( ) = 0;
};

#endif // COLLECTION_H

---