Pure vs. Impure Iterators in Go

a year ago

Go has standardized iterators with the introduction of generics in Go 1.18, enhancing flexibility and performance.
Iterators in Go can be classified into 'pure' (stateless, no observable side effects) and 'impure' (stateful, with side effects).
The official documentation introduces 'single-use iterators' as a subcategory of impure iterators, but this classification is seen as ambiguous and imprecise.
Pure iterators are easier to reason about and can reduce heap allocations, making them preferable from a performance standpoint.
However, consistency with related iterators (like those in the bytes package) may necessitate the use of impure iterators in some cases.
The Go community is still establishing conventions around iterators, with ongoing discussions about terminology and best practices.

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