Boost C++ Libraries

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Boost.Python

Header <boost/python/stl_iterator.hpp>

Contents

Introduction
Classes
Class template stl_input_iterator
Class stl_input_iterator synopsis
Class template stl_input_iterator constructors
Class template stl_input_iterator modifiers
Class template stl_input_iterator observers
Examples

Introduction

<boost/python/stl_iterator.hpp> provides types for creating C++ Iterators from Python iterables.

Classes

Class Template stl_input_iterator

Instances of stl_input_iterator<T> hold a Python iterator and adapt it for use with STL algorithms. stl_input_iterator<T> satisfies the requirements for an Input Iterator.

Template Parameter Requirements Semantics Default
ValueType ValueType must be CopyConstructible. Dereferencing an instance of stl_input_iterator<ValueType> will return an rvalue of type ValueType. None

Class Template stl_input_iterator synopsis

namespace boost { namespace python
{
  template <class ValueType>
  struct stl_input_iterator
  {
      typedef std::ptrdiff_t difference_type;
      typedef ValueType value_type;
      typedef ValueType* pointer;
      typedef ValueType reference;
      typedef std::input_iterator_tag iterator_category;

      stl_input_iterator();
      stl_input_iterator(object const& ob);

      stl_input_iterator& operator++();
      stl_input_iterator operator++(int);

      ValueType operator*() const;

      friend bool operator==(stl_input_iterator const& lhs, stl_input_iterator const& rhs);
      friend bool operator!=(stl_input_iterator const& lhs, stl_input_iterator const& rhs);
  private:
      object it; // For exposition only
      object ob; // For exposition only
  };
}}

Class Template stl_input_iterator constructors 

stl_input_iterator()
Effects: Creates a past-the-end input iterator, useful for signifying the end of a sequence.
Postconditions: this is past-the-end.
Throws: Nothing.
stl_input_iterator(object const& ob)
Effects: Calls ob.attr("__iter__")() and stores the resulting Python iterator object in this->it. Then, calls this->it.attr("next")() and stores the result in this->ob. If the sequence is exhausted, sets this->ob to object().
Postconditions: this is a dereferenceable or past-the-end.

Class Template stl_input_iterator modifiers 

stl_input_iterator& operator++()
Effects: Calls this->it.attr("next")() and stores the result in this->ob. If the sequence is exhausted, sets this->ob to object().
Postconditions: this is a dereferenceable or past-the-end.
Returns: *this.
stl_input_iterator operator++(int)
Effects: stl_input_iterator tmp = *this; ++*this; return tmp;
Postconditions: this is a dereferenceable or past-the-end.

Class Templatestl_input_iterator observers

ValueType operator*() const
Effects: Returns the current element in the sequence.
Returns: extract<ValueType>(this->ob); 
friend bool operator==(stl_input_iterator const& lhs, stl_input_iterator const& rhs)
Effects: Returns true if both iterators are dereferenceable or if both iterators are past-the-end, false otherwise.
Returns: (lhs.ob == object()) == (rhs.ob == object()) 
friend bool operator!=(stl_input_iterator const& lhs, stl_input_iterator const& rhs)
Effects: Returns false if both iterators are dereferenceable or if both iterators are past-the-end, true otherwise.
Returns: !(lhs == rhs)

Examples

#include <boost/python/object.hpp>
#include <boost/python/stl_iterator.hpp>

#include <list>

using namespace boost::python;
std::list<int> sequence_to_int_list(object const& ob)
{
    stl_input_iterator<int> begin(ob), end;
    return std::list<int>(begin, end);
}

Revised 30 October, 2005

© Copyright Eric Niebler 2005.