Select a predicate based on the parameter types.

Used in: An ASSERT_PRED(pred, ...), often together with crpcut::abs_diff, crpcut::relative_diff, crpcut::ulps_diff or crpcut::regex.

crpcut::match<matcher>(...) can create a predicate by instantiating an object of type depending on the type of the parameters.

For example, crpcut::match<crpcut::abs_diff>(1.0) instantiates an object of type crpcut::abs_diff::type<double>, whereas crpcut::match<crpcut::abs_diff>(1.0f) instantiates an object of type crpcut::abs_diff::type<float>.

By default, crpcut::match<matcher> instantiates an object of type matcher, but this can be changed by specializing the template crpcut::match_traits. For example, crpcut::abs_diff uses the specialization

    namespace crpcut {
      template <typename T>
      struct match_traits<abs_diff, T>
      {
        typedef typename abs_diff::template type<T> type;
      };
    }

where, of course, crpcut::abs_diff::type<T> is the actual predicate used in comparisons.

match_traits can be specialized with up to 10 template parameters.