eve::comparisons< T > Struct Template Reference

Extension point for ordering and equality computation. More...

#include <eve/traits/comparisons.hpp>

Detailed Description

template<typename T>
struct eve::comparisons< T >

Required header: #include <eve/traits/comparisons.hpp>

eve::comparisons is an extension point for user-defined product type that may requires specific equality or ordering computations. It is meant to be specialized on scalar user-defined type to provide a set of class function members performing said operations.

To be considered valid, a specialization of eve::comparisons should provide either/or :

• Functions called equal and not_equal that take an eve::callable_options and two values of the product type.
• Functions called less, less_equal, greater and greater_equal that take an eve::callable_options and two values of the product type

Depending on the set of functions provided, said type will be said to satisfy either the eve::has_equality_support and/or the eve::has_ordering_support concept.

Template Parameters

T	Type to process

Example

#include <iostream>
#include <eve/eve.hpp>
 
namespace udt
{
  struct point : eve::struct_support<point, int, float> {};
}
 
// Specialize eve::comparisons so that only position is used for equality
template<> struct eve::comparisons<udt::point>
{
  static constexpr auto equal(auto const& a, auto const& b) noexcept
  {
    return eve::is_equal(get<0>(a), get<0>(b));
  }
 
  static constexpr auto not_equal(auto const& a, auto const& b) noexcept
  {
    return eve::is_not_equal(get<0>(a), get<0>(b));
  }
};
 
int main()
{
  eve::wide<float, eve::fixed<8>> a{1.2,2.3,3.4,4.5,5.6,6.7,7.8,8.9}, b{0.2,0.2,0.4,0.4,0.6,0.6,0.7,0.7};
  eve::wide<int  , eve::fixed<8>> i{1,2,3,4,5,6,7,8};
 
  auto p1 = eve::zip(eve::as<udt::point>{}, i,a);
  auto p2 = eve::zip(eve::as<udt::point>{},i,b);
  std::cout << p1         << "\n";
  std::cout << p2         << "\n";
  std::cout << "p1 == p2                  : " <<  (p1 == p2) << "\n";
  std::cout << "p1 != p2                  : " <<  (p1 != p2) << "\n";
  std::cout << "eve::is_equal(p1, p2)     : " << eve::is_equal(p1, p2) << "\n";
  std::cout << "eve::is_not_equal(p1, p2) : " << eve::is_not_equal(p1, p2) << "\n";
}