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use crate::{Consumer, Iterable, IterableSeq}; #[must_use = "iterable adaptors are lazy and do nothing unless consumed"] #[derive(Debug, Clone)] pub struct LazyMap<I, F> { pub(crate) iterable: I, pub(crate) f: F, } impl<I, F, T> Iterable for LazyMap<I, F> where I: Iterable, F: Fn(I::Item) -> T, { type C = I::CC<T>; type CC<U> = I::CC<U>; type F = I::CF<T>; type CF<U> = I::CF<U>; } impl<I, F, T> IterableSeq for LazyMap<I, F> where I: IterableSeq, F: Fn(I::Item) -> T, { } impl<I, F, T> Consumer for LazyMap<I, F> where I: Consumer, F: Fn(I::Item) -> T, { type Item = T; type IntoIter = std::iter::Map<I::IntoIter, F>; fn consume(self) -> Self::IntoIter { self.iterable.consume().map(self.f) } } #[cfg(test)] mod tests { use super::*; use crate::assert_type; use crate::lazy::collect; #[test] fn smoke() { let v = vec![1, 2, 3]; let res = collect(v.lazy_map(|i| i.to_string())); assert_eq!(res, vec!["1".to_string(), "2".to_string(), "3".to_string()]); } #[test] fn test_f() { let v = [1, 2, 3]; let res = v.lazy_map(|i| i.to_string()).rev(); assert_type::<[String; 3]>(res); } #[test] fn test_cf() { let v = [1, 2, 3]; let res = v .lazy_map(|i| i.to_string()) .map(|s| s.parse::<u32>().unwrap()); assert_type::<[u32; 3]>(res); } }