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/*
* Copyright 2008-2013 NVIDIA Corporation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*! \file thrust/iterator/constant_iterator.h
* \brief An iterator which returns a constant value when
* dereferenced
*/
#pragma once
#include <thrust/detail/config.h>
#include <thrust/iterator/detail/constant_iterator_base.h>
#include <thrust/iterator/iterator_facade.h>
THRUST_NAMESPACE_BEGIN
/*! \addtogroup iterators
* \{
*/
/*! \addtogroup fancyiterator Fancy Iterators
* \ingroup iterators
* \{
*/
/*! \p constant_iterator is an iterator which represents a pointer into a range
* of constant values. This iterator is useful for creating a range filled with the same
* value without explicitly storing it in memory. Using \p constant_iterator saves both
* memory capacity and bandwidth.
*
* The following code snippet demonstrates how to create a \p constant_iterator whose
* \c value_type is \c int and whose value is \c 10.
*
* \code
* #include <thrust/iterator/constant_iterator.h>
*
* thrust::constant_iterator<int> iter(10);
*
* *iter; // returns 10
* iter[0]; // returns 10
* iter[1]; // returns 10
* iter[13]; // returns 10
*
* // and so on...
* \endcode
*
* This next example demonstrates how to use a \p constant_iterator with the
* \p thrust::transform function to increment all elements of a sequence by the
* same value. We will create a temporary \p constant_iterator with the function
* \p make_constant_iterator function in order to avoid explicitly specifying
* its type:
*
* \code
* #include <thrust/iterator/constant_iterator.h>
* #include <thrust/transform.h>
* #include <thrust/functional.h>
* #include <thrust/device_vector.h>
*
* int main()
* {
* thrust::device_vector<int> data(4);
* data[0] = 3;
* data[1] = 7;
* data[2] = 2;
* data[3] = 5;
*
* // add 10 to all values in data
* thrust::transform(data.begin(), data.end(),
* thrust::make_constant_iterator(10),
* data.begin(),
* thrust::plus<int>());
*
* // data is now [13, 17, 12, 15]
*
* return 0;
* }
* \endcode
*
* \see make_constant_iterator
*/
template<typename Value,
typename Incrementable = use_default,
typename System = use_default>
class constant_iterator
: public detail::constant_iterator_base<Value, Incrementable, System>::type
{
/*! \cond
*/
friend class thrust::iterator_core_access;
typedef typename detail::constant_iterator_base<Value, Incrementable, System>::type super_t;
typedef typename detail::constant_iterator_base<Value, Incrementable, System>::incrementable incrementable;
typedef typename detail::constant_iterator_base<Value, Incrementable, System>::base_iterator base_iterator;
public:
typedef typename super_t::reference reference;
typedef typename super_t::value_type value_type;
/*! \endcond
*/
/*! Null constructor initializes this \p constant_iterator's constant using its
* null constructor.
*/
__host__ __device__
constant_iterator()
: super_t(), m_value() {}
/*! Copy constructor copies the value of another \p constant_iterator into this
* \p constant_iterator.
*
* \p rhs The constant_iterator to copy.
*/
__host__ __device__
constant_iterator(constant_iterator const &rhs)
: super_t(rhs.base()), m_value(rhs.m_value) {}
/*! Copy constructor copies the value of another \p constant_iterator with related
* System type.
*
* \param rhs The \p constant_iterator to copy.
*/
template<typename OtherSystem>
__host__ __device__
constant_iterator(constant_iterator<Value,Incrementable,OtherSystem> const &rhs,
typename thrust::detail::enable_if_convertible<
typename thrust::iterator_system<constant_iterator<Value,Incrementable,OtherSystem> >::type,
typename thrust::iterator_system<super_t>::type
>::type * = 0)
: super_t(rhs.base()), m_value(rhs.value()) {}
/*! This constructor receives a value to use as the constant value of this
* \p constant_iterator and an index specifying the location of this
* \p constant_iterator in a sequence.
*
* \p v The value of this \p constant_iterator's constant value.
* \p i The index of this \p constant_iterator in a sequence. Defaults to the
* value returned by \c Incrementable's null constructor. For example,
* when <tt>Incrementable == int</tt>, \c 0.
*/
__host__ __device__
constant_iterator(value_type const& v, incrementable const &i = incrementable())
: super_t(base_iterator(i)), m_value(v) {}
/*! This constructor is templated to allow construction from a value type and
* incrementable type related this this \p constant_iterator's respective types.
*
* \p v The value of this \p constant_iterator's constant value.
* \p i The index of this \p constant_iterator in a sequence. Defaults to the
* value returned by \c Incrementable's null constructor. For example,
* when <tt>Incrementable == int</tt>, \c 0.
*/
template<typename OtherValue, typename OtherIncrementable>
__host__ __device__
constant_iterator(OtherValue const& v, OtherIncrementable const& i = incrementable())
: super_t(base_iterator(i)), m_value(v) {}
/*! This method returns the value of this \p constant_iterator's constant value.
* \return A \c const reference to this \p constant_iterator's constant value.
*/
__host__ __device__
Value const& value() const
{ return m_value; }
/*! \cond
*/
protected:
__host__ __device__
Value const& value_reference() const
{ return m_value; }
__host__ __device__
Value & value_reference()
{ return m_value; }
private: // Core iterator interface
__host__ __device__
reference dereference() const
{
return m_value;
}
private:
Value m_value;
/*! \endcond
*/
}; // end constant_iterator
/*! This version of \p make_constant_iterator creates a \p constant_iterator
* from values given for both value and index. The type of \p constant_iterator
* may be inferred by the compiler from the types of its parameters.
*
* \param x The value of the returned \p constant_iterator's constant value.
* \param i The index of the returned \p constant_iterator within a sequence.
* The type of this parameter defaults to \c int. In the default case,
* the value of this parameter is \c 0.
*
* \return A new \p constant_iterator with constant value & index as given
* by \p x & \p i.
*
* \see constant_iterator
*/
template<typename ValueT, typename IndexT>
inline __host__ __device__
constant_iterator<ValueT, IndexT> make_constant_iterator(ValueT x, IndexT i = int())
{
return constant_iterator<ValueT, IndexT>(x, i);
} // end make_constant_iterator()
/*! This version of \p make_constant_iterator creates a \p constant_iterator
* using only a parameter for the desired constant value. The value of the
* returned \p constant_iterator's index is set to \c 0.
*
* \param x The value of the returned \p constant_iterator's constant value.
* \return A new \p constant_iterator with constant value equal to \p x and
* index equal to \c 0.
* \see constant_iterator
*/
template<typename V>
inline __host__ __device__
constant_iterator<V> make_constant_iterator(V x)
{
return constant_iterator<V>(x, 0);
} // end make_constant_iterator()
/*! \} // end fancyiterators
*/
/*! \} // end iterators
*/
THRUST_NAMESPACE_END
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