The quote means to not assume something is slow, but to actually measure it. Pure Functional Programmers state that you should not even measure performance. Th

The quote means to not assume something is slow, but to actually measure it. Pure Functional Programmers state that you should not even measure performance. They take this position because despite their many claims that Pure FP is performant, it turns out that if you measure it, it’s not performant. Hence “don’t measure”.