Iterator Adapters

A report needs the first 3 paid orders from a list of 100,000 orders, and half of those orders are paid. Code that builds a slice of paid orders and then takes the first 3 calls its paid check 100,000 times and allocates memory 26 times. The same logic written with iterators calls the paid check 5 times and allocates memory 3 times.

A program further down this page measured both versions on one machine. The difference comes from when each step runs. The slice code finishes each step before the next one begins