Attachment 143 Details for Bug 99 – new proof of concept creating and storing evaluators, not expressions

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new proof of concept creating and storing evaluators, not expressions

proof_of_concept_v2.cpp (text/plain), 1.76 KB, created by Gael Guennebaud on 2011-03-18 19:23:22 UTC

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Creator: Gael Guennebaud

Created: 2011-03-18 19:23:22 UTC

Size: 1.76 KB

patch

obsolete

>#include <iostream>
>
>struct Matrix
>{
>  Matrix() { data = new int[4]; }
>  ~Matrix() { delete[] data; }
>  Matrix(const Matrix& m) { std::cerr << "COPY\n"; }
>  typedef const Matrix& Nested;
>  int* data;//[4];
>};
>
>template<typename A, typename B> struct Plus
>{
>  typedef const Plus Nested;
>  Plus(const A& a, const B& b) : m_a(a), m_b(b) {}
>  typename A::Nested m_a;
>  typename B::Nested m_b;
>};
>
>template<typename A, typename B> struct Product
>{
>  typedef const Product Nested;
>  Product(const A& a, const B& b) : m_a(a), m_b(b) {}
>  typename A::Nested m_a;
>  typename B::Nested m_b;
>};
>
>template<typename T> struct evaluator {};
>
>template<> struct evaluator<Matrix>
>{
>  evaluator(const Matrix& m) : m_m(m) {}
>  int coeff(int i) const { return m_m.data[i]; }
>  const Matrix& m_m;
>};
>
>template<typename A, typename B> struct evaluator<Plus<A,B> >
>{
>  evaluator(const Plus<A,B>& plus) : m_lhs(plus.m_a), m_rhs(plus.m_b) {}
>  int coeff(int i) const { return m_lhs.coeff(i) + m_rhs.coeff(i); }
>  evaluator<A> m_lhs;
>  evaluator<B> m_rhs;
>};
>
>template<typename A, typename B> struct evaluator<Product<A,B> >
>{
>  evaluator(const Product<A,B>& plus) : m_lhs(plus.m_a), m_rhs(plus.m_b)
>  {
>    for(int i=0;i<4;++i)
>      res.data[i] = m_lhs.coeff(i) * m_rhs.coeff(i);
>  }
>  int coeff(int i) const { return res.data[i]; }
>  Matrix res;
>  evaluator<A> m_lhs;
>  evaluator<B> m_rhs;
>};
>
>int main()
>{
>  Matrix a, b, c, d;
>  for (int i=0;i<4;++i)
>  {
>    a.data[i] = i+10;
>    b.data[i] = i+20;
>    c.data[i] = i+30;
>    d.data[i] = i+40;
>  }
>  typedef Plus<Matrix, Plus<Matrix, Product<Matrix,Matrix> > > Xpr;
>  Xpr xpr(a,Plus<Matrix,Product<Matrix,Matrix> >(b,Product<Matrix,Matrix>(c,d) ) );
>  evaluator<Xpr> eval(xpr);
>  for (int i=0;i<4;++i)
>    std::cout << eval.coeff(i) << " ";
>  std::cout << "\n";
>  return 0;
>}

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