util::count_extracted_types< Extractor, Target, Tuple > Struct Template Reference

Counts the elements of a tuple-like type containing a Target type. More...

#include <TupleLookupByTag.h>

Inheritance diagram for util::count_extracted_types< Extractor, Target, Tuple >:

Detailed Description

template<template< typename T, typename...> class Extractor, typename Target, typename Tuple>
struct util::count_extracted_types< Extractor, Target, Tuple >

Counts the elements of a tuple-like type containing a Target type.

Template Parameters

Extractor	trait exposing the target type in an element
Target	the target type to be counted
Tuple	the tuple-like type to be investigated

See Also

count_extracted_types_v, index_of_extracted_type, has_extracted_type, count_types

Given a tuple-like type Tuple, this trait returns how many of its elements "contain" the target type Target. For example:

template <typename T>
struct ExtractValueType { using type = typename T::value_type; };

using tuple_t
  = std::tuple<std::vector<float>, std::vector<int>, std::list<int>>;

constexpr unsigned int nIntegerContainers
  = util::count_extracted_types<ExtractValueType, int, tuple_t>();
constexpr unsigned int nDoubleContainers
  = util::count_extracted_types<ExtractValueType, double, tuple_t>();
constexpr unsigned int nFloatContainers
  = util::count_extracted_types<ExtractValueType, float, tuple_t>();

nIntegerContainers will hold value 2, meaning there are two types with int as value_type. Likewise, nDoubleContainers will be 1 and nFloatContainers will be 0.

Definition at line 524 of file TupleLookupByTag.h.

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The documentation for this struct was generated from the following file:

• TupleLookupByTag.h