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Slice_iter.h

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#ifndef ATLFAST_SLICEITER_H
#define ATLFAST_SLICEITER_H
#include <valarray>

//=================================================
//
// Slice_iter
//
//  from Sjoustrup's "the C++ programming language" ch 22.4.6
//


namespace Atlfast {
  using std::valarray;
  using std::slice;

  template<class T> class Slice_iter{
    valarray<T>* v;
    slice s;
    size_t curr;   //index of current element
    T& ref(size_t i) const {return (*v)[s.start()+i*s.stride()];}
  public:
    Slice_iter(valarray<T>* vv, slice ss): v(vv), s(ss), curr(0){}
    Slice_iter end() const{
      Slice_iter t = *this;
      t.curr=s.size();
      return t;
    }
    Slice_iter& operator++(){curr++; return *this;}
    Slice_iter  operator++(int){Slice_iter t=*this; curr++; return t;}
    
    T& operator[] (size_t i) {return ref(i); }    //C style subscript  
    T& operator() (size_t i) {return ref(i); }    //Fortran style subscript  
    T& operator*()           {return ref(curr); } //current element

    friend
      bool operator==(const Slice_iter<T>& p, const Slice_iter<T>& q){
      //      bool operator==<>(const Slice_iter<T>& p, const Slice_iter<T>& q){
      return 
        p.curr==q.curr && 
        p.s.stride()==q.s.stride() && 
        p.s.start() == q.s.start();
    }
    
    friend
      bool operator!=(const Slice_iter<T>& p, const Slice_iter<T>& q){
      //      bool operator!=<>(const Slice_iter<T>& p, const Slice_iter<T>& q){
      return  (!p==q);
    }
    
    friend
      bool operator< (const Slice_iter<T>& p, const Slice_iter<T>& q){
      //      bool operator< <>(const Slice_iter<T>& p, const Slice_iter<T>& q){
      return 
        p.curr<q.curr && 
        p.s.stride() == q.s.stride() && 
        p.s.start()  == q.s.start();
    }
    
  };
}//namespace
#endif

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