Compile Time Fibonacci

What this compile-time C++ metaprogramming problem tests

This is a hard C++ coding problem that probes deep knowledge of template metaprogramming—specifically, your ability to compute values at compile time rather than runtime. It is representative of the kind of problem high-frequency trading firms and systems-programming teams use to assess whether a candidate understands C++ templates as a Turing-complete computation system.

The challenge is to implement a template-based solution that evaluates the Fibonacci sequence entirely during compilation, with the result embedded as a compile-time constant. This requires understanding recursive template instantiation, template specialization, and how to encode iterative or memoized logic within the type system. Strong solutions recognize that naive recursive templates can lead to exponential instantiation overhead, and thus employ techniques like partial specialization or helper metafunctions to optimize the computation.

• Template specialization and base cases
• Recursive template instantiation
• Compile-time constant evaluation with static_assert
• Performance implications of template recursion depth