123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145 |
- // Copyright (C) 2016-2018 T. Zachary Laine
- //
- // Distributed under the Boost Software License, Version 1.0. (See
- // accompanying file LICENSE_1_0.txt or copy at
- // http://www.boost.org/LICENSE_1_0.txt)
- //[ vector
- #include <boost/yap/yap.hpp>
- #include <vector>
- #include <iostream>
- //[ vector_take_nth_xform
- struct take_nth
- {
- template <typename T>
- auto operator() (boost::yap::expr_tag<boost::yap::expr_kind::terminal>,
- std::vector<T> const & vec)
- { return boost::yap::make_terminal(vec[n]); }
- std::size_t n;
- };
- //]
- // A stateful transform that records whether all the std::vector<> terminals
- // it has seen are equal to the given size.
- struct equal_sizes_impl
- {
- template <typename T>
- auto operator() (boost::yap::expr_tag<boost::yap::expr_kind::terminal>,
- std::vector<T> const & vec)
- {
- auto const expr_size = vec.size();
- if (expr_size != size)
- value = false;
- return 0;
- }
- std::size_t const size;
- bool value;
- };
- template <typename Expr>
- bool equal_sizes (std::size_t size, Expr const & expr)
- {
- equal_sizes_impl impl{size, true};
- boost::yap::transform(boost::yap::as_expr(expr), impl);
- return impl.value;
- }
- // Assigns some expression e to the given vector by evaluating e elementwise,
- // to avoid temporaries and allocations.
- template <typename T, typename Expr>
- std::vector<T> & assign (std::vector<T> & vec, Expr const & e)
- {
- decltype(auto) expr = boost::yap::as_expr(e);
- assert(equal_sizes(vec.size(), expr));
- for (std::size_t i = 0, size = vec.size(); i < size; ++i) {
- vec[i] = boost::yap::evaluate(
- boost::yap::transform(boost::yap::as_expr(expr), take_nth{i}));
- }
- return vec;
- }
- // As assign() above, just using +=.
- template <typename T, typename Expr>
- std::vector<T> & operator+= (std::vector<T> & vec, Expr const & e)
- {
- decltype(auto) expr = boost::yap::as_expr(e);
- assert(equal_sizes(vec.size(), expr));
- for (std::size_t i = 0, size = vec.size(); i < size; ++i) {
- vec[i] += boost::yap::evaluate(
- boost::yap::transform(boost::yap::as_expr(expr), take_nth{i}));
- }
- return vec;
- }
- // Define a type trait that identifies std::vectors.
- template <typename T>
- struct is_vector : std::false_type {};
- template <typename T, typename A>
- struct is_vector<std::vector<T, A>> : std::true_type {};
- // Define all the expression-returning numeric operators we need. Each will
- // accept any std::vector<> as any of its arguments, and then any value in the
- // remaining argument, if any -- some of the operators below are unary.
- BOOST_YAP_USER_UDT_UNARY_OPERATOR(negate, boost::yap::expression, is_vector); // -
- BOOST_YAP_USER_UDT_ANY_BINARY_OPERATOR(multiplies, boost::yap::expression, is_vector); // *
- BOOST_YAP_USER_UDT_ANY_BINARY_OPERATOR(divides, boost::yap::expression, is_vector); // /
- BOOST_YAP_USER_UDT_ANY_BINARY_OPERATOR(modulus, boost::yap::expression, is_vector); // %
- BOOST_YAP_USER_UDT_ANY_BINARY_OPERATOR(plus, boost::yap::expression, is_vector); // +
- BOOST_YAP_USER_UDT_ANY_BINARY_OPERATOR(minus, boost::yap::expression, is_vector); // -
- BOOST_YAP_USER_UDT_ANY_BINARY_OPERATOR(less, boost::yap::expression, is_vector); // <
- BOOST_YAP_USER_UDT_ANY_BINARY_OPERATOR(greater, boost::yap::expression, is_vector); // >
- BOOST_YAP_USER_UDT_ANY_BINARY_OPERATOR(less_equal, boost::yap::expression, is_vector); // <=
- BOOST_YAP_USER_UDT_ANY_BINARY_OPERATOR(greater_equal, boost::yap::expression, is_vector); // >=
- BOOST_YAP_USER_UDT_ANY_BINARY_OPERATOR(equal_to, boost::yap::expression, is_vector); // ==
- BOOST_YAP_USER_UDT_ANY_BINARY_OPERATOR(not_equal_to, boost::yap::expression, is_vector); // !=
- BOOST_YAP_USER_UDT_ANY_BINARY_OPERATOR(logical_or, boost::yap::expression, is_vector); // ||
- BOOST_YAP_USER_UDT_ANY_BINARY_OPERATOR(logical_and, boost::yap::expression, is_vector); // &&
- BOOST_YAP_USER_UDT_ANY_BINARY_OPERATOR(bitwise_and, boost::yap::expression, is_vector); // &
- BOOST_YAP_USER_UDT_ANY_BINARY_OPERATOR(bitwise_or, boost::yap::expression, is_vector); // |
- BOOST_YAP_USER_UDT_ANY_BINARY_OPERATOR(bitwise_xor, boost::yap::expression, is_vector); // ^
- int main()
- {
- int i;
- int const n = 10;
- std::vector<int> a,b,c,d;
- std::vector<double> e(n);
- for (i = 0; i < n; ++i)
- {
- a.push_back(i);
- b.push_back(2*i);
- c.push_back(3*i);
- d.push_back(i);
- }
- // After this point, no allocations occur.
- assign(b, 2);
- assign(d, a + b * c);
- a += if_else(d < 30, b, c);
- assign(e, c);
- e += e - 4 / (c + 1);
- for (i = 0; i < n; ++i)
- {
- std::cout
- << " a(" << i << ") = " << a[i]
- << " b(" << i << ") = " << b[i]
- << " c(" << i << ") = " << c[i]
- << " d(" << i << ") = " << d[i]
- << " e(" << i << ") = " << e[i]
- << std::endl;
- }
- return 0;
- }
- //]
|