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Auto merge of #45379 - cuviper:unit_from_iter, r=alexcrichton
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impl FromIterator<()> for ()

This just collapses all unit items from an iterator into one.  This is
more useful when combined with higher-level abstractions, like
collecting to a `Result<(), E>` where you only care about errors:

```rust
use std::io::*;
data = vec![1, 2, 3, 4, 5];
let res: Result<()> = data.iter()
    .map(|x| writeln!(stdout(), "{}", x))
    .collect();
assert!(res.is_ok());
```
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bors committed Nov 8, 2017
2 parents ee22861 + 68d05b2 commit e177df3
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1 change: 1 addition & 0 deletions src/libcore/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -189,3 +189,4 @@ pub mod fmt;
mod char_private;
mod iter_private;
mod tuple;
mod unit;
31 changes: 31 additions & 0 deletions src/libcore/unit.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,31 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use iter::FromIterator;

/// Collapses all unit items from an iterator into one.
///
/// This is more useful when combined with higher-level abstractions, like
/// collecting to a `Result<(), E>` where you only care about errors:
///
/// ```
/// use std::io::*;
/// let data = vec![1, 2, 3, 4, 5];
/// let res: Result<()> = data.iter()
/// .map(|x| writeln!(stdout(), "{}", x))
/// .collect();
/// assert!(res.is_ok());
/// ```
#[stable(feature = "unit_from_iter", since = "1.23.0")]
impl FromIterator<()> for () {
fn from_iter<I: IntoIterator<Item=()>>(iter: I) -> Self {
iter.into_iter().for_each(|()| {})
}
}

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