Acts/EventData/MeasurementHelpers.hpp

0001 // This file is part of the ACTS project.
0002 //
0003 // Copyright (C) 2016 CERN for the benefit of the ACTS project
0004 //
0005 // This Source Code Form is subject to the terms of the Mozilla Public
0006 // License, v. 2.0. If a copy of the MPL was not distributed with this
0007 // file, You can obtain one at https://mozilla.org/MPL/2.0/.
0008
0009 #pragma once
0010
0011 #include "Acts/Definitions/TrackParametrization.hpp"
0012 #include "Acts/Utilities/Helpers.hpp"
0013
0014 #include <cstddef>
0015
0016 namespace Acts {
0017
0018 namespace detail {
0019 /// Helper functor for @c visit_measurement. This is the actual functor given
0020 /// to @c template_switch.
0021 /// @tparam I Compile time int value
0022 template <std::size_t I>
0023 struct visit_measurement_callable {
0024   /// The invoked function. It will perform the head/top-left corner
0025   /// extraction, and pass thee results to the given lambda.
0026   /// @tparam L The lambda type
0027   /// @tparam A The parameter vector type
0028   /// @tparam B The covariance matrix type
0029   /// @note No requirements on @c A and @c B are made, to enable a single
0030   /// overload for both const and non-const matrices/vectors.
0031   /// @param param The parameter vector
0032   /// @param cov The covariance matrix
0033   /// @param lambda The lambda to call with the statically sized subsets
0034   template <typename L, typename A, typename B>
0035   auto static constexpr invoke(A&& param, B&& cov, L&& lambda) {
0036     return lambda(param.template head<I>(), cov.template topLeftCorner<I, I>());
0037   }
0038 };
0039 }  // namespace detail
0040
0041 /// Dispatch a lambda call on an overallocated parameter vector and covariance
0042 /// matrix, based on a runtime dimension value. Inside the lambda call, the
0043 /// vector and matrix will have fixed dimensions, but will still point back to
0044 /// the originally given overallocated values.
0045 /// @tparam L The lambda type
0046 /// @tparam A The parameter vector type
0047 /// @tparam B The covariance matrix type
0048 /// @note No requirements on @c A and @c B are made, to enable a single
0049 /// overload for both const and non-const matrices/vectors.
0050 /// @param param The parameter vector
0051 /// @param cov The covariance matrix
0052 /// @param dim The actual dimension as a runtime value
0053 /// @param lambda The lambda to call with the statically sized subsets
0054 template <typename L, typename A, typename B>
0055 auto visit_measurement(A&& param, B&& cov, std::size_t dim, L&& lambda) {
0056   return template_switch<detail::visit_measurement_callable, 1, eBoundSize>(
0057       dim, param, cov, lambda);
0058 }
0059
0060 /// Dispatch a generic lambda on a measurement dimension. This overload doesn't
0061 /// assume anything about what is needed inside the lambda, it communicates the
0062 /// dimension via an integral constant type
0063 /// @tparam L The generic lambda type to call
0064 /// @param dim The runtime dimension of the measurement
0065 /// @param lambda The generic lambda instance to call
0066 /// @param args Additional arguments passed to @p lambda
0067 /// @return Returns the lambda return value
0068 template <typename L, typename... Args>
0069 auto visit_measurement(std::size_t dim, L&& lambda, Args&&... args) {
0070   return template_switch_lambda<1, eBoundSize>(dim, lambda,
0071                                                std::forward<Args>(args)...);
0072 }
0073
0074 }  // namespace Acts