58 lines
1.5 KiB
Rust
58 lines
1.5 KiB
Rust
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// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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#![feature(transpose_result)]
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#[derive(Copy, Clone, Debug, PartialEq)]
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struct BadNumErr;
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fn try_num(x: i32) -> Result<i32, BadNumErr> {
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if x <= 5 {
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Ok(x + 1)
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} else {
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Err(BadNumErr)
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}
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}
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type ResOpt = Result<Option<i32>, BadNumErr>;
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type OptRes = Option<Result<i32, BadNumErr>>;
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fn main() {
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let mut x: ResOpt = Ok(Some(5));
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let mut y: OptRes = Some(Ok(5));
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assert_eq!(x, y.transpose());
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assert_eq!(x.transpose(), y);
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x = Ok(None);
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y = None;
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assert_eq!(x, y.transpose());
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assert_eq!(x.transpose(), y);
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x = Err(BadNumErr);
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y = Some(Err(BadNumErr));
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assert_eq!(x, y.transpose());
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assert_eq!(x.transpose(), y);
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let res: Result<Vec<i32>, BadNumErr> =
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(0..10)
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.map(|x| {
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let y = try_num(x)?;
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Ok(if y % 2 == 0 {
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Some(y - 1)
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} else {
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None
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})
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})
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.filter_map(Result::transpose)
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.collect();
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assert_eq!(res, Err(BadNumErr))
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}
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