jj_lib/
iter_util.rs

1// Copyright 2025 The Jujutsu Authors
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7// https://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15//! Iterator helpers.
16
17/// Returns `Ok(true)` if any element satisfies the fallible predicate,
18/// `Ok(false)` if none do. Returns `Err` on the first error encountered.
19pub fn fallible_any<T, E>(
20    iter: impl IntoIterator<Item = T>,
21    mut predicate: impl FnMut(T) -> Result<bool, E>,
22) -> Result<bool, E> {
23    for item in iter {
24        if predicate(item)? {
25            return Ok(true);
26        }
27    }
28    Ok(false)
29}
30
31/// Returns `Ok(Some(item))` for the first element where the predicate returns
32/// `Ok(true)`, `Ok(None)` if no element satisfies it, or `Err` on the first
33/// error.
34pub fn fallible_find<T, E>(
35    iter: impl IntoIterator<Item = T>,
36    mut predicate: impl FnMut(&T) -> Result<bool, E>,
37) -> Result<Option<T>, E> {
38    for item in iter {
39        if predicate(&item)? {
40            return Ok(Some(item));
41        }
42    }
43    Ok(None)
44}
45
46/// Returns `Ok(Some(index))` for the first element where the predicate returns
47/// `Ok(true)`, `Ok(None)` if no element satisfies it, or `Err` on the first
48/// error.
49pub fn fallible_position<T, E>(
50    iter: impl IntoIterator<Item = T>,
51    mut predicate: impl FnMut(T) -> Result<bool, E>,
52) -> Result<Option<usize>, E> {
53    for (index, item) in iter.into_iter().enumerate() {
54        if predicate(item)? {
55            return Ok(Some(index));
56        }
57    }
58    Ok(None)
59}
jj_lib/iter_util.rs

jj_lib/
iter_util.rs
