Compile-time map and inverse map values

by

In this C++11 solution all map items are kept in constexpr array and there are constexpr recursive functions to search by either key or value.

#include <utility>

using Item = std::pair<int, int>;
constexpr Item map_items[] = {
    { 6, 7 },
    { 10, 12 },
    { 300, 5000 },
};
constexpr auto map_size = sizeof map_items/sizeof map_items[0];

static constexpr int findValue(int key, int range = map_size) {
    return
            (range == 0) ? throw "Key not present":
            (map_items[range - 1].first == key) ? map_items[range - 1].second:
            findValue(key, range - 1);
};

static constexpr int findKey(int value, int range = map_size) {
    return
            (range == 0) ? throw "Value not present":
            (map_items[range - 1].second == value) ? map_items[range - 1].first:
            findKey(value, range - 1);
};

static_assert(findKey(findValue(10)) == 10, "should be inverse");

More Related Contents:

  1. c++ push reference node to stl list
  2. Why should the implementation and the declaration of a template class be in the same header file? [duplicate]
  3. Variadic template pack expansion
  4. Is there any advantage of using map over unordered_map in case of trivial keys?
  5. initializer_list and template type deduction
  6. How do I explicitly instantiate a template function?
  7. C++ Get name of type in template
  8. Implicit type conversion with template
  9. Why doesn’t a derived template class have access to a base template class’ identifiers?
  10. C++ SFINAE examples?
  11. What are Mixins (as a concept)
  12. What is the default constructor for C++ pointer?
  13. Template partial ordering – why does partial deduction succeed here
  14. Matching alias template as template argument
  15. multiple definition of template specialization when using different objects
  16. C++ Loop through Map
  17. Undefined reference error for template method [duplicate]
  18. How do compilers treat variable length arrays
  19. Templated class specialization where template argument is a template
  20. How Does std::enable_if work?
  21. c++ –
  22. details of std::make_index_sequence and std::index_sequence
  23. ‘auto’ as a template argument placeholder for a function parameter
  24. Calculating and printing factorial at compile time in C++
  25. Specializing function template for reference types
  26. What would a std::map extended initializer list look like?
  27. Why Can’t I store references in a `std::map` in C++?
  28. c++ standard practice: virtual interface classes vs. templates
  29. Conditional compilation based on template values?
  30. How to test whether class B is derived from template family of classes

Leave a Comment