How close can pure functional programming get to C?

The author explores the limitations of functional programming in achieving the performance of C by analyzing the implementation of a simple program in both languages. They found that with careful optimization, functional programming can get very close to the performance of C, but there are still some differences in performance and memory usage. The author suggests that this is because functional programming is based on a different set of assumptions about the nature of computation and data, which can lead to different performance characteristics.