现在我正在尝试教 g++ 编译器线性代数，以便 g++ 可以重写表达式，例如(matrix * vector)(index)用于评估表达式的循环。基本上，这就是我所期望的作为“富有表现力的 C++ ”系列最后一篇文章的下一篇文章。上一篇文章解释了如何制作用于添加向量的 EDSL，因此我编写了另一个用于将矩阵乘以向量的 EDSL。
但是当我自己的矩阵和向量类的 Proto 域的名称作为第一个宏参数传递时，无法编译 BOOST_PROTO_DEFINE_OPERATORS 宏。
所以我想知道 Proto 转换是否有可能评估矩阵和向量对象的混合表达式。似乎没有可以编译的示例代码，Proto 用户指南 1.57.0中“将现有类型适配到 Proto”中的示例代码虽然是关于如何将现有矩阵和向量类型适配到 Proto，但并不完整。
我很茫然..你能给我一些建议或提示吗？
这是我的源代码。如果您能建议我如何解决它，我将不胜感激：
#include <iostream>
#include <boost/proto/proto.hpp>
namespace mpl = boost::mpl;
namespace proto = boost::proto;
namespace LinAlg {
class Vector;
class Matrix;
// Functor for lazy evaluation
struct ElmOfMatVecMult;
// The grammar for an expression like ( matrix * vector )(index)
struct MatVecMultElmGrammar : proto::or_<
proto::when< proto::multiplies< Matrix, Vector>,
proto::_make_function( ElmOfMatVecMult,
proto::_left, proto::_right,
proto::_state) >
> {};
// The grammar for a vector expression
// ( Now I consider just one form : matrix * vector . )
struct VecExprGrammar : proto::or_<
proto::when< proto::function< MatVecMultElmGrammar, proto::_>,
MatVecMultElmGrammar( proto::_left, proto::_right) >,
proto::multiplies< Matrix, Vector>
> {};
template<typename E> struct Expr;
// The above grammar is associated with this domain.
struct Domain
: proto::domain<proto::generator<Expr>, VecExprGrammar>
{};
// A wrapper template for linear algebraic expressions
// including matrices and vectors
template<typename ExprType>
struct Expr
: proto::extends<ExprType, Expr<ExprType>, Domain>
{
explicit Expr(const ExprType& e)
: proto::extends<ExprType, Expr<ExprType>, Domain>(e)
{}
};
// Testing if data in an heap array can be a vector object
class Vector {
private:
int sz;
double* data;
public:
template <typename Sig> struct result;
template <typename This, typename T>
struct result< This(T) > { typedef double type; };
typedef double result_type;
explicit Vector(int sz_ = 1, double iniVal = 0.0) :
sz( sz_), data( new double[sz] ) {
for (int i = 0; i < sz; i++) data[i] = iniVal;
std::cout << "Created" << std::endl;
}
Vector(const Vector& vec) :
sz( vec.sz), data( new double[sz] ) {
for (int i = 0; i < sz; i++) data[i] = vec.data[i];
std::cout << "Copied! " << std::endl;
}
~Vector() {
delete [] data;
std::cout << "Deleted" << std::endl;
}
// accessing to an element of this vector
double& operator()(int i) { return data[i]; }
const double& operator()(int i) const { return data[i]; }
};
// Testing if data in an heap array can be a matrix object
class Matrix
{
private:
int rowSz, colSz;
double* data;
double** m;
public:
template <typename Signature> struct result;
template <typename This, typename T>
struct result< This(T,T) > { typedef double type; };
explicit Matrix(int rowSize = 1, int columnSize =1,
double iniVal = 0.0) :
rowSz( rowSize), colSz(columnSize),
data( new double[rowSz*colSz] ), m( new double*[rowSz])
{
for (int i = 0; i < rowSz; i++) m[i] = data + i*colSz;
for (int ri = 0; ri < rowSz; ri++)
for (int ci = 0; ci < colSz; ci++) m[ri][ci] = iniVal;
std::cout << "Created" << std::endl;
}
Matrix(const Matrix& mat) :
rowSz( mat.rowSz), colSz( mat.colSz),
data( new double[rowSz*colSz] ), m( new double*[rowSz])
{
for (int i = 0; i < rowSz; i++) m[i] = data + i*colSz;
for (int ri = 0; ri < rowSz; ri++)
for (int ci = 0; ci < colSz; ci++)
m[ri][ci] = mat.m[ri][ci];
std::cout << "Copied! " << std::endl;
}
~Matrix()
{
delete [] m;
delete [] data;
std::cout << "Deleted" << std::endl;
}
int rowSize() const { return rowSz; }
int columnSize() const { return colSz; }
// accesing to a vector element
double& operator()(int ri, int ci) { return m[ri][ci]; }
const double& operator()(int ri, int ci) const { return m[ri][ci]; }
};
// An expression like ( matrix * vector )(index) is transformed
// into the loop for calculating the dot product between
// the vector and matrix.
struct ElmOfMatVecMult
{
double operator()( Matrix const& mat, Vector const& vec,
int index) const
{
double elm = 0.0;
for (int ci =0; ci < mat.columnSize(); ci++)
elm += mat(index, ci) * vec(ci);
return elm;
}
};
// Define a trait for detecting linear algebraic terminals, to be used
// by the BOOST_PROTO_DEFINE_OPERATORS macro below.
template<typename> struct IsExpr : mpl::false_ {};
template<> struct IsExpr< Vector> : mpl::true_ {};
template<> struct IsExpr< Matrix> : mpl::true_ {};
// This defines all the overloads to make expressions involving
// Vector and Matrix objects to build Proto's expression templates.
BOOST_PROTO_DEFINE_OPERATORS(IsExpr, Domain)
}
int main()
{
using namespace LinAlg;
proto::_default<> trans;
Matrix mat( 3, 3);
Vector vec1(3);
mat(0,0) = 1.00; mat(0,1) = 1.01; mat(0,2) = 1.02;
mat(1,0) = 1.10; mat(1,1) = 1.11; mat(1,2) = 1.12;
mat(2,0) = 1.20; mat(2,1) = 1.21; mat(2,2) = 1.22;
vec1(0) = 1.0;
vec1(1) = 2.0;
vec1(2) = 3.0;
proto::display_expr( ( mat * vec1)(2) );
proto::display_expr( VecExprGrammar()( ( mat * vec1)(2) );
double vecElm = trans( VecExprGrammar()( ( mat * vec1)(2) );
return 0;
}