RDFHelpers.hxx

Go to the documentation of this file.

// Author: Enrico Guiraud, Danilo Piparo CERN  02/2018

/*************************************************************************
 * Copyright (C) 1995-2018, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/

// This header contains helper free functions that slim down RDataFrame's programming model

#ifndef ROOT_RDF_HELPERS
#define ROOT_RDF_HELPERS

#include <ROOT/TypeTraits.hxx>

#include <algorithm> // std::transform
#include <functional>
#include <iterator> // std::back_inserter
#include <stdexcept>
#include <string>
#include <type_traits>
#include <vector>

namespace ROOT {
namespace Internal {
template <typename... ArgTypes, typename F>
std::function<bool(ArgTypes...)> NotHelper(ROOT::TypeTraits::TypeList<ArgTypes...>, F &&f)
{
   return std::function<bool(ArgTypes...)>([=](ArgTypes... args) mutable { return !f(args...); });
}

template <typename... ArgTypes, typename Ret, typename... Args>
std::function<bool(ArgTypes...)> NotHelper(ROOT::TypeTraits::TypeList<ArgTypes...>, Ret (*f)(Args...))
{
   return std::function<bool(ArgTypes...)>([=](ArgTypes... args) mutable { return !f(args...); });
}
} // namespace Internal


namespace RDF {
// clag-format off
/// Given a callable with signature bool(T1, T2, ...) return a callable with same signature that returns the negated
/// result
///
/// The callable must have one single non-template definition of operator(). This is a limitation with respect to
/// std::not_fn, required for interoperability with RDataFrame.
// clang-format on
template <typename F,
          typename Args = typename ROOT::TypeTraits::CallableTraits<typename std::decay<F>::type>::arg_types_nodecay,
          typename Ret = typename ROOT::TypeTraits::CallableTraits<typename std::decay<F>::type>::ret_type>
auto Not(F &&f) -> decltype(ROOT::Internal::NotHelper(Args(), std::forward<F>(f)))
{
   static_assert(std::is_same<Ret, bool>::value, "RDF::Not requires a callable that returns a bool.");
   return ROOT::Internal::NotHelper(Args(), std::forward<F>(f));
}

} // namespace RDF

} // namespace ROOT
#endif