rust / intermediate
Snippet
Iterator Adaptors and Lazy Evaluation
Rust iterators use lazy evaluation, meaning operations are not executed until consumed by a terminal operation like 'collect', 'sum', or 'for_each'. This allows chaining multiple adaptors like filter, map, skip, and take without intermediate allocations. Iterator adaptors transform the iterator without consuming it, and flat_map can expand each element into multiple values.
snippet.rs
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fn main() {let numbers = vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10];let result: Vec<i32> = numbers.iter().filter(|&&x| x % 2 == 0).map(|x| x * x).skip(1).take(2).collect();println!("Result: {:?}", result);let sum_of_squares: i32 = numbers.iter().filter(|&&x| x > 3).map(|x| x * x).sum();println!("Sum of squares (x > 3): {}", sum_of_squares);let chained: Vec<i32> = (1..=5).flat_map(|x| std::iter::repeat(x).take(x)).collect();println!("FlatMap result: {:?}", chained);}
Breakdown
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.iter()
Creates a non-consuming iterator over the vector reference
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.filter(|&&x| x % 2 == 0)
Predicate closure keeping only even numbers; &&x needed to dereference &&i32
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.map(|x| x * x)
Transforms each element by squaring it
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.skip(1).take(2)
Skips first element, then takes next two elements from filtered stream
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.collect()
Terminal operation consuming iterator and collecting into a Vec
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.flat_map(|x| std::iter::repeat(x).take(x))
Maps each x to x copies of itself, flattening into single sequence