Implementing tuple_find – A Constexpr-Compatible Algorithm for std::tuple in Modern C++

Most STL algorithms work great with homogeneous containers like std::vector or std::array. But what about heterogeneous ones like std::tuple?

In this article, I present an implementation of tuple_find – a constexpr-friendly algorithm that searches for a specific value in a std::tuple and returns a reference to the found element, along with its position. It handles both const and non-const references and supports multiple matches by allowing the search to continue from a given index.

This is the second part of a short series on algorithms for heterogeneous containers. The first part covered tuple_for_each, a generic iteration algorithm for std::tuple.

Features of tuple_find:

• Works with std::tuple of arbitrary types

• Returns a reference to the found value (as std::variant inside std::optional)

• Preserves const-ness of the matched element

• Supports repeated search using an optional start index

• Fully constexpr capable (C++20+)

• Avoids dangling references through compile-time checks

Example: Find and modify elements

int a{20}, b{10}, c{10}, d{30};
auto tpl = std::tie(a, b, c, d);

size_t idx = 0;
while (true) {
  auto result = tuple_find(tpl, 10, idx);
  if (!result) break;
  auto& ref = std::get<0>(*result); // non-const reference
  ref.first += 100;
  idx = ref.second + 1;
}

After running this, b and c will both be 110.

Example: constexpr usage

static constexpr int x{10}, y{20}, z{30};
constexpr auto tpl = std::tie(x, y, z);
constexpr auto result = tuple_find(tpl, 10);

static_assert(result && std::get<1>(*result).second == 0);

This post gives a brief overview of the idea and usage.

👉 Full explanation, design decisions, limitations, and implementation details are available here:

🔗 Implementing 'tuple_find' – A Constexpr-Compatible Algorithm for Heterogeneous Containers

Let me know if you’ve used something similar or see room for improvement – feedback is always welcome.