This is always a fun corner of programming terminology to me. A ton of dense, mathy code like hash computation, de/serialization, sin/cos computation, etc. is

This is always a fun corner of programming terminology to me. A ton of dense, mathy code like hash computation, de/serialization, sin/cos computation, etc. is usually best implemented in a memory efficient C-style way but lends itself to be used in a very functional way; inputs and outputs without any retained state or side effects. I think that subtlety is hard to articulate and gets lost.