Extra-Conditionals-with-Match-Guards.cpp

#include "matchit.h"
#include <iostream>
#include <optional>
using namespace matchit;

void sample1()
{
  auto const num = std::make_optional(4);

  Id<int32_t> x;
  match(num)(
      pattern | some(x.at(_ < 5)) =
          [&]
      { std::cout << "less than five: " << *x << std::endl; },
      pattern | some(x) = [&]
      { std::cout << *x << std::endl; },
      pattern | none = [&] {});
}

template <typename T>
std::ostream &operator<<(std::ostream &o, std::optional<T> const &op)
{
  if (op)
  {
    o << *op;
  }
  else
  {
    o << "none";
  }
  return o;
}

void sample2()
{
  auto const x = std::make_optional(5);
  auto const y = 10;

  Id<int32_t> n;
  match(x)(
      // clang-format off
        pattern | some(50)             = [&]{ std::cout << "Got 50" << std::endl; },
        // In `match(it)`, you can use variable inside patterns, just like literals.
        pattern | some(y)              = [&]{ std::cout << "Matched, n = " << *n << std::endl; },
        pattern | _                    = [&]{ std::cout << "Default case, x = " << x << std::endl; }
      // clang-format on
  );

  std::cout << "at the end: x = " << x << ", y = " << y << std::endl;
}

void sample3()
{
  auto const x = 4;
  auto const y = false;

  std::cout << match(x)(
                   // clang-format off
            pattern | or_(4, 5, 6) | when(expr(y)) = expr("yes"),
            pattern | _                            = expr("no")
                   // clang-format on
                   )
            << std::endl;
}

int32_t main()
{
  sample1();
  sample2();
  sample3();
  return 0;
}