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.