1[#getting_started_17]
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3 template <class L, char Op, class R> struct eval_binary_op;
4 template <class L, class R> struct eval_binary_op<L, '+', R> : boost::mpl::plus<L, R>::type {};
5 template <class L, class R> struct eval_binary_op<L, '-', R> : boost::mpl::minus<L, R>::type {};
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