Compile-Time Sorting in C++ With Templates: Why Heapsort Falls Apart

Tried implementing sorting algorithms as pure template metaprogramming. Not constexpr , not consteval . The old way, where the compiler does the sorting during template instantiation and the "output" is a type. Quicksort worked. Mergesort worked. Heapsort turned into selection sort. That last part took me longer to understand than I'd like to admit. The setup Everything operates on a type like arr . There's no runtime array. The sorted result is another type, like arr , and you verify it with st