Rust Tutorial: How to Build Custom Iterators Using the Iterator Trait

A new entry in a Rust programming guide series explains how to create custom iterators by implementing the Iterator trait, which requires only a single method: next. The tutorial walks through building a Counter struct that iterates from 1 to 5 by incrementing an internal count field and returning None once the limit is reached. It then demonstrates a more advanced use case that chains multiple iterator methods — zip, map, filter, and sum — across two Counter instances to compute a final result of 18. Key iterator adaptor methods are explained individually, covering how zip pairs elements from two iterators, map transforms them, and filter selects only those divisible by 3. The guide is part of a broader chapter on functional programming features in Rust, including closures and iterator performance.