rivet

rivet is a library to create range adaptor(closure) for the original view type.

header only
single file
cross platform
- GCC 10 or later
- MSVC 2019 or later
- clang 15(libc++ only), 16 or later

This library is only for C++20 or later.

Usage

Copy include/rivet.hpp somewhere, reference it from your project, and include rivet.hpp.

Example

After inclusion of the header(rivet.hpp), rivet::range_adaptor_base<Derived>(for range adaptor) or rivet::range_adaptor_closure_base<Derived>(for range adaptor closure) is used in the public inheritance by CRTP.

Range Adoptor

Example of a unique implementation of views::filter, the range adaptor.

#include "rivet.hpp"

namespace myranges::views {
  namespace detail {
    
    // Define adapter type and CRTP
    struct filter_adaptor: public rivet::range_adaptor_base<filter_adaptor> {

      // Range Adoptor main process. Generates the original view.
      // Always defined in `operator() const`.
      template<std::ranges::viewable_range R, typename Pred>
      constexpr auto operator()(R&& r, Pred&& p) const {
        return std::ranges::filter_view(std::forward<R>(r), std::forward<Pred>(p));
      }

      // It is a hassle, but essential.
      RIVET_USING_BASEOP;
    };
  }

  // My views::filter(Range adaptor object) difinition.
  inline constexpr detail::filter_adaptor filter;
}

Range Adoptor Closure

Example of a unique implementation of views::common, the range adaptor closure.

#include "rivet.hpp"

namespace myranges::views {
  namespace detail {

    // Define adapter closure type and CRTP
    // In this case, specify true after the type name(common_adaptor_closure) to make it clear that it is range adaptor closure.
    struct common_adaptor_closure : public rivet::range_adaptor_closure_base<common_adaptor_closure> {

      // Range Adoptor Closure main process. Generates the original view.
      // Always defined in `operator() const`.
      template<std::ranges::viewable_range R>
      constexpr auto operator()(R&& r) const {
        if constexpr (std::ranges::common_range<R>) {
          return std::views::all(std::forward<R>(r));
        } else {
          return std::ranges::common_view(std::forward<R>(r));
        }
      }
    };

  }

  // My views::common(Range adaptor closure object) difinition.
  inline constexpr detail::common_adaptor_closure common;
}

Alternate syntax with lambdas

#include "rivet.hpp"

namespace myranges::views {

  // My views::filter(Range adaptor object) difinition.
  inline constexpr rivet::adaptor filter = []<std::ranges::viewable_range R, typename Pred>(R &&r, Pred &&p) {
    // Range Adoptor main process. Generates the original view.
    return std::ranges::filter_view(std::forward<R>(r), std::forward<Pred>(p));
  };

  // My views::common(Range adaptor closure object) difinition.
  inline constexpr rivet::closure common = []<std::ranges::viewable_range R>(R &&r) {
    // Range Adoptor Closure main process. Generates the original view.
    if constexpr (std::ranges::common_range<R>)  {
      return std::views::all(std::forward<R>(r));
    } else {
      return std::ranges::common_view(std::forward<R>(r));
    }
  };
}

Range adaptor (closure) object can be defined by simply passing a lambda expression describing the process of generating your own view to rivet::adaptor(for adaptor) or rivet::closure(for adaptor closure).

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