TMatRowsIterator_decl.h

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// -*- C++ -*-

// PLearn (A C++ Machine Learning Library)
// Copyright (C) 1998 Pascal Vincent
// Copyright (C) 1999-2002 Pascal Vincent, Yoshua Bengio and University of Montreal
//

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// modification, are permitted provided that the following conditions are met:
// 
//  1. Redistributions of source code must retain the above copyright
//     notice, this list of conditions and the following disclaimer.
// 
//  2. Redistributions in binary form must reproduce the above copyright
//     notice, this list of conditions and the following disclaimer in the
//     documentation and/or other materials provided with the distribution.
// 
//  3. The name of the authors may not be used to endorse or promote
//     products derived from this software without specific prior written
//     permission.
// 
// THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
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/* *******************************************************      
   * $Id: TMatRowsIterator_decl.h,v 1.1 2004/04/17 00:44:55 plearner Exp $
   * AUTHORS: Pascal Vincent & Yoshua Bengio
   * This file is part of the PLearn library.
   ******************************************************* */


#ifndef TMatRowsIterator_decl_INC
#define TMatRowsIterator_decl_INC

namespace PLearn {
using namespace std;

template <class T>
class TMatRowsIterator
{
public:
  typedef random_access_iterator_tag iterator_category;
  typedef TVec<T>                    value_type;
  typedef ptrdiff_t                  difference_type;
  typedef TVec<T>*                   pointer;
  typedef TVec<T>&                   reference;
  
private:
  T* ptr;                                    
  int width;                                 
  int mod;                                   

public:
  TMatRowsIterator()
    : ptr(), width(), mod() {}

  TMatRowsIterator(T* p, int w, int m)
    : ptr(p), width(w), mod(m) {}

  // Implement trivial iterator functions
  bool operator==(const TMatRowsIterator& other) const {
    return ptr == other.ptr && width == other.width && mod == other.mod;
  }

  bool operator!=(const TMatRowsIterator& y)
  { return !operator==(y); }

  value_type operator*() {
    return TVec<T>(width, ptr);
  }

  // cannot define operator-> here since we cannot return a pointer to a
  // temporary (e.g. stack-based) vector and expect this to work properly...
  
  // Implement forward iterator functions
  TMatRowsIterator& operator++() {
    ptr += mod;
    return *this;
  }

  TMatRowsIterator operator++(int) {
    TMatRowsIterator r(*this);
    ptr += mod;
    return r;
  }

  // Implement bidirectional iterator functions
  TMatRowsIterator& operator--() {
    ptr -= mod;
    return *this;
  }

  TMatRowsIterator operator--(int) {
    TMatRowsIterator r(*this);
    ptr -= mod;
    return r;
  }

  // Implement random access iterator functions
  TMatRowsIterator& operator+=(difference_type n) {
    ptr += n*mod;
    return *this;
  }

  TMatRowsIterator operator+(difference_type n) {
    TMatRowsIterator r(*this);
    r += n;
    return r;
  }
  
  TMatRowsIterator& operator-=(difference_type n) {
    ptr -= n*mod;
    return *this;
  }

  TMatRowsIterator operator-(difference_type n) {
    TMatRowsIterator r(*this);
    r -= n;
    return r;
  }

  difference_type operator-(const TMatRowsIterator& y) {
    return (ptr - y.ptr) / mod;
  }
  
  value_type operator[](difference_type n) {
    return TVec<T>(width, ptr + n*mod);
  }

  bool operator<(const TMatRowsIterator& y) {
    return ptr < y.ptr;
  }

};

} // end of namespace PLearn

#endif

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