diff --git a/src/adaptors/mod.rs b/src/adaptors/mod.rs index 127edaa56..b2956d222 100644 --- a/src/adaptors/mod.rs +++ b/src/adaptors/mod.rs @@ -1159,6 +1159,55 @@ impl Iterator for MapResults } } +/// An iterator adapter to apply a fallible transformation within a nested `Result`. +/// +/// See [`.try_map_results()`](../trait.Itertools.html#method.try_map_results) for more information. +#[must_use = "iterator adaptors are lazy and do nothing unless consumed"] +pub struct TryMapResults { + iter: I, + f: F +} + +/// Create a new `TryMapResults` iterator. +pub fn try_map_results(iter: I, f: F) -> TryMapResults + where I: Iterator>, + F: FnMut(T) -> Result +{ + TryMapResults { + iter: iter, + f: f, + } +} + +impl Iterator for TryMapResults + where I: Iterator>, + F: FnMut(T) -> Result +{ + type Item = Result; + + fn next(&mut self) -> Option { + self.iter.next().map(|v| v.and_then(&mut self.f)) + } + + fn size_hint(&self) -> (usize, Option) { + self.iter.size_hint() + } + + fn fold(self, init: Acc, mut fold_f: Fold) -> Acc + where Fold: FnMut(Acc, Self::Item) -> Acc, + { + let mut f = self.f; + self.iter.fold(init, move |acc, v| fold_f(acc, v.and_then(&mut f))) + } + + fn collect(self) -> C + where C: FromIterator + { + let mut f = self.f; + self.iter.map(move |v| v.and_then(&mut f)).collect() + } +} + /// An iterator adapter to get the positions of each element that matches a predicate. /// /// See [`.positions()`](../trait.Itertools.html#method.positions) for more information. diff --git a/src/lib.rs b/src/lib.rs index e4671921c..0c26f6b02 100644 --- a/src/lib.rs +++ b/src/lib.rs @@ -59,6 +59,7 @@ pub mod structs { Batching, Step, MapResults, + TryMapResults, Merge, MergeBy, TakeWhileRef, @@ -635,6 +636,24 @@ pub trait Itertools : Iterator { adaptors::map_results(self, f) } + /// Return an iterator adaptor that applies the provided fallible + /// closure to every `Result::Ok` value. `Result::Err` values in + /// the original iterator are unchanged. + /// + /// ``` + /// use itertools::Itertools; + /// + /// let input = vec![Ok(41), Err(false), Ok(i32::max_value())]; + /// let it = input.into_iter().try_map_results(|i| i.checked_add(1).ok_or(true)); + /// itertools::assert_equal(it, vec![Ok(42), Err(false), Err(true)]); + /// ``` + fn try_map_results(self, f: F) -> TryMapResults + where Self: Iterator> + Sized, + F: FnMut(T) -> Result, + { + adaptors::try_map_results(self, f) + } + /// Return an iterator adaptor that merges the two base iterators in /// ascending order. If both base iterators are sorted (ascending), the /// result is sorted.