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G26_CRTP_1.cpp
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G26_CRTP_1.cpp
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/**************************************************************************************************
*
* \file G26_CRTP_1.cpp
* \brief Guideline 26: Use CRTP to Introduce Static Type Categories
*
* Copyright (C) 2022 Klaus Iglberger - All Rights Reserved
*
* This file is part of the supplemental material for the O'Reilly book "C++ Software Design"
* (https://www.oreilly.com/library/view/c-software-design/9781098113155/).
*
**************************************************************************************************/
//---- <DenseVector.h> ----------------------------------------------------------------------------
#include <cmath>
#include <numeric>
#include <ostream>
template< typename Derived >
struct DenseVector
{
constexpr Derived& derived() noexcept { return static_cast<Derived&>(*this); }
constexpr Derived const& derived() const noexcept { return static_cast<Derived const&>(*this); }
constexpr size_t size() const noexcept { return derived().size(); }
decltype(auto) operator[]( size_t index ) noexcept { return derived()[index]; }
decltype(auto) operator[]( size_t index ) const noexcept { return derived()[index]; }
decltype(auto) begin() noexcept { return derived().begin(); }
decltype(auto) begin() const noexcept { return derived().begin(); }
decltype(auto) end() noexcept { return derived().end(); }
decltype(auto) end() const noexcept { return derived().end(); }
};
template< typename Derived >
std::ostream& operator<<( std::ostream& os, DenseVector<Derived> const& vector )
{
size_t const size( vector.size() );
os << "(";
for( size_t i=0UL; i<size; ++i ) {
os << " " << vector[i];
}
os << " )";
return os;
}
template< typename Derived >
decltype(auto) l2norm( DenseVector<Derived> const& vector )
{
using T = typename Derived::value_type;
return std::sqrt( std::inner_product( std::begin(vector), std::end(vector)
, std::begin(vector), T{} ) );
}
//---- <DynamicVector.h> --------------------------------------------------------------------------
//#include <DenseVector.h>
#include <vector>
#include <initializer_list>
template< typename T >
class DynamicVector
: public DenseVector< DynamicVector<T> >
{
public:
using value_type = T;
using iterator = typename std::vector<T>::iterator;
using const_iterator = typename std::vector<T>::const_iterator;
DynamicVector() = default;
DynamicVector( std::initializer_list<T> init )
: values_( std::begin(init), std::end(init) )
{}
size_t size() const noexcept { return values_.size(); }
T& operator[]( size_t index ) noexcept { return values_[index]; }
T const& operator[]( size_t index ) const noexcept { return values_[index]; }
iterator begin() noexcept { return values_.begin(); }
const_iterator begin() const noexcept { return values_.begin(); }
iterator end() noexcept { return values_.end(); }
const_iterator end() const noexcept { return values_.end(); }
// ... Many numeric functions
private:
std::vector<T> values_;
};
//---- <StaticVector.h> ---------------------------------------------------------------------------
//#include <DenseVector.h>
#include <array>
#include <initializer_list>
template< typename T, size_t Size >
class StaticVector
: public DenseVector< StaticVector<T,Size> >
{
public:
using value_type = T;
using iterator = typename std::array<T,Size>::iterator;
using const_iterator = typename std::array<T,Size>::const_iterator;
StaticVector() = default;
StaticVector( std::initializer_list<T> init )
{
std::copy( std::begin(init), std::end(init), std::begin(values_) );
}
size_t size() const noexcept { return values_.size(); }
T& operator[]( size_t index ) noexcept { return values_[index]; }
T const& operator[]( size_t index ) const noexcept { return values_[index]; }
iterator begin() noexcept { return values_.begin(); }
const_iterator begin() const noexcept { return values_.begin(); }
iterator end() noexcept { return values_.end(); }
const_iterator end() const noexcept { return values_.end(); }
// ... Many numeric functions
private:
std::array<T,Size> values_;
};
//---- <Main.cpp> ---------------------------------------------------------------------------------
//#include <DynamicVector.h>
//#include <StaticVector.h>
#include <cstdlib>
#include <iostream>
int main()
{
DynamicVector<int> const a{ 1, 2, 3 };
StaticVector<int,4UL> const b{ 4, 5, 6, 7 };
std::cout << "\n"
<< " a = " << a << ", L2-norm = " << l2norm(a) << "\n"
<< " b = " << b << ", L2-norm = " << l2norm(b) << "\n"
<< "\n";
return EXIT_SUCCESS;
}