74 lines
2.4 KiB
Rust
74 lines
2.4 KiB
Rust
//
|
|
// imag - the personal information management suite for the commandline
|
|
// Copyright (C) 2015, 2016 Matthias Beyer <mail@beyermatthias.de> and contributors
|
|
//
|
|
// This library is free software; you can redistribute it and/or
|
|
// modify it under the terms of the GNU Lesser General Public
|
|
// License as published by the Free Software Foundation; version
|
|
// 2.1 of the License.
|
|
//
|
|
// This library is distributed in the hope that it will be useful,
|
|
// but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
// Lesser General Public License for more details.
|
|
//
|
|
// You should have received a copy of the GNU Lesser General Public
|
|
// License along with this library; if not, write to the Free Software
|
|
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
|
//
|
|
|
|
/// Folds its contents to a result.
|
|
pub trait FoldResult: Sized {
|
|
type Item;
|
|
|
|
/// Apply a `FnMut(Self::Item) -> Result<R, E>` to each item. If each
|
|
/// application returns an `Ok(_)`, return `Ok(())`, indicating success.
|
|
/// Otherwise return the first error.
|
|
///
|
|
/// The return type of this function only indicates success with the
|
|
/// `Ok(())` idiom. To retrieve the values of your application, include an
|
|
/// accumulator in `func`. This is the intended reason for the permissive
|
|
/// `FnMut` type.
|
|
fn fold_result<R, E, F>(self, func: F) -> Result<(), E>
|
|
where F: FnMut(Self::Item) -> Result<R, E>;
|
|
|
|
}
|
|
|
|
impl<X, I: Iterator<Item = X>> FoldResult for I {
|
|
type Item = X;
|
|
|
|
fn fold_result<R, E, F>(self, mut func: F) -> Result<(), E>
|
|
where F: FnMut(Self::Item) -> Result<R, E>
|
|
{
|
|
for item in self {
|
|
try!(func(item));
|
|
}
|
|
Ok(())
|
|
}
|
|
}
|
|
|
|
#[test]
|
|
fn test_fold_result_success() {
|
|
let v = vec![1, 2, 3];
|
|
let mut accum = vec![];
|
|
let result: Result<(), &str> = v.iter().fold_result(|item| {
|
|
accum.push(*item * 2);
|
|
Ok(*item)
|
|
});
|
|
assert_eq!(result, Ok(()));
|
|
assert_eq!(accum, vec![2, 4, 6]);
|
|
}
|
|
|
|
#[test]
|
|
fn test_fold_result_failure() {
|
|
let v: Vec<usize> = vec![1, 2, 3];
|
|
let mut accum: Vec<usize> = vec![];
|
|
let result: Result<(), &str> = v.iter().fold_result(|item| if *item == 2 {
|
|
Err("failure")
|
|
} else {
|
|
accum.push(*item * 2);
|
|
Ok(*item)
|
|
});
|
|
assert_eq!(result, Err("failure"));
|
|
assert_eq!(accum, vec![2]);
|
|
}
|