Beartype: Unbearably fast runtime type checking in Python

> Beartype brings Rust- and C++-inspired zero-cost abstractions

> Thanks to aggressive memoization and dynamic code generation at decoration time, beartype guarantees O(1) non-amortized worst-case runtime complexity with negligible constant factors.

I don't think the author(s) understands what "zero-cost abstraction means". O(1) is not O(0). Also let's not forget that memoization incurs a memory cost.