436 lines
12 KiB
Rust
436 lines
12 KiB
Rust
// Copyright 2012 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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//! A type that represents one of two alternatives
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#[allow(missing_doc)];
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use option::{Some, None};
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use option;
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use clone::Clone;
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use container::Container;
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use cmp::Eq;
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use iter::{Iterator, FilterMap};
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use result::Result;
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use result;
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use str::StrSlice;
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use vec;
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use vec::{OwnedVector, ImmutableVector};
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/// `Either` is a type that represents one of two alternatives
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#[deriving(Clone, Eq, IterBytes)]
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pub enum Either<L, R> {
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Left(L),
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Right(R)
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}
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impl<L, R> Either<L, R> {
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/// Applies a function based on the given either value
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///
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/// If `value` is `Left(L)` then `f_left` is applied to its contents, if
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/// `value` is `Right(R)` then `f_right` is applied to its contents, and the
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/// result is returned.
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#[inline]
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pub fn either<T>(&self, f_left: &fn(&L) -> T, f_right: &fn(&R) -> T) -> T {
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match *self {
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Left(ref l) => f_left(l),
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Right(ref r) => f_right(r)
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}
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}
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/// Flips between left and right of a given `Either`
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#[inline]
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pub fn flip(self) -> Either<R, L> {
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match self {
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Right(r) => Left(r),
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Left(l) => Right(l)
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}
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}
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/// Checks whether the given value is a `Left`
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#[inline]
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pub fn is_left(&self) -> bool {
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match *self {
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Left(_) => true,
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_ => false
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}
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}
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/// Checks whether the given value is a `Right`
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#[inline]
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pub fn is_right(&self) -> bool {
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match *self {
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Right(_) => true,
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_ => false
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}
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}
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/// Retrieves the value from a `Left`.
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/// Fails with a specified reason if the `Either` is `Right`.
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#[inline]
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pub fn expect_left(self, reason: &str) -> L {
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match self {
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Left(x) => x,
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Right(_) => fail!("{}", reason.to_owned())
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}
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}
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/// Retrieves the value from a `Left`. Fails if the `Either` is `Right`.
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#[inline]
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pub fn unwrap_left(self) -> L {
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self.expect_left("called Either::unwrap_left()` on `Right` value")
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}
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/// Retrieves the value from a `Right`.
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/// Fails with a specified reason if the `Either` is `Left`.
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#[inline]
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pub fn expect_right(self, reason: &str) -> R {
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match self {
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Right(x) => x,
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Left(_) => fail!("{}", reason.to_owned())
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}
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}
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/// Retrieves the value from a `Right`. Fails if the `Either` is `Left`.
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#[inline]
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pub fn unwrap_right(self) -> R {
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self.expect_right("called Either::unwrap_right()` on `Left` value")
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}
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}
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/// A generic trait for converting a value to a `Either`
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pub trait ToEither<L, R> {
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/// Convert to the `either` type
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fn to_either(&self) -> Either<L, R>;
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}
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/// A generic trait for converting a value to a `Either`
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pub trait IntoEither<L, R> {
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/// Convert to the `either` type
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fn into_either(self) -> Either<L, R>;
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}
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/// A generic trait for converting a value to a `Either`
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pub trait AsEither<L, R> {
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/// Convert to the `either` type
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fn as_either<'a>(&'a self) -> Either<&'a L, &'a R>;
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}
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impl<L, R: Clone> option::ToOption<R> for Either<L, R> {
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#[inline]
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fn to_option(&self)-> option::Option<R> {
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match *self {
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Left(_) => None,
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Right(ref r) => Some(r.clone()),
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}
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}
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}
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impl<L, R> option::IntoOption<R> for Either<L, R> {
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#[inline]
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fn into_option(self)-> option::Option<R> {
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match self {
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Left(_) => None,
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Right(r) => Some(r),
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}
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}
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}
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impl<L, R> option::AsOption<R> for Either<L, R> {
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#[inline]
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fn as_option<'a>(&'a self) -> option::Option<&'a R> {
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match *self {
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Left(_) => None,
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Right(ref r) => Some(r),
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}
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}
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}
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impl<L: Clone, R: Clone> result::ToResult<R, L> for Either<L, R> {
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#[inline]
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fn to_result(&self)-> result::Result<R, L> {
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match *self {
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Left(ref l) => result::Err(l.clone()),
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Right(ref r) => result::Ok(r.clone()),
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}
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}
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}
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impl<L, R> result::IntoResult<R, L> for Either<L, R> {
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#[inline]
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fn into_result(self)-> result::Result<R, L> {
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match self {
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Left(l) => result::Err(l),
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Right(r) => result::Ok(r),
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}
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}
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}
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impl<L, R> result::AsResult<R, L> for Either<L, R> {
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#[inline]
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fn as_result<'a>(&'a self) -> result::Result<&'a R, &'a L> {
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match *self {
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Left(ref l) => result::Err(l),
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Right(ref r) => result::Ok(r),
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}
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}
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}
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impl<L: Clone, R: Clone> ToEither<L, R> for Either<L, R> {
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fn to_either(&self) -> Either<L, R> { self.clone() }
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}
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impl<L, R> IntoEither<L, R> for Either<L, R> {
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fn into_either(self) -> Either<L, R> { self }
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}
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impl<L, R> AsEither<L, R> for Either<L, R> {
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fn as_either<'a>(&'a self) -> Either<&'a L, &'a R> {
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match *self {
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Left(ref l) => Left(l),
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Right(ref r) => Right(r),
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}
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}
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}
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/// An iterator yielding the `Left` values of its source
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pub type Lefts<L, R, Iter> = FilterMap<'static, Either<L, R>, L, Iter>;
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/// An iterator yielding the `Right` values of its source
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pub type Rights<L, R, Iter> = FilterMap<'static, Either<L, R>, R, Iter>;
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/// Extracts all the left values
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pub fn lefts<L, R, Iter: Iterator<Either<L, R>>>(eithers: Iter)
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-> Lefts<L, R, Iter> {
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do eithers.filter_map |elt| {
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match elt {
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Left(x) => Some(x),
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_ => None,
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}
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}
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}
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/// Extracts all the right values
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pub fn rights<L, R, Iter: Iterator<Either<L, R>>>(eithers: Iter)
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-> Rights<L, R, Iter> {
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do eithers.filter_map |elt| {
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match elt {
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Right(x) => Some(x),
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_ => None,
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}
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}
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}
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// FIXME: #8228 Replaceable by an external iterator?
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/// Extracts from a vector of either all the left values and right values
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///
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/// Returns a structure containing a vector of left values and a vector of
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/// right values.
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pub fn partition<L, R>(eithers: ~[Either<L, R>]) -> (~[L], ~[R]) {
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let n_lefts = eithers.iter().count(|elt| elt.is_left());
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let mut lefts = vec::with_capacity(n_lefts);
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let mut rights = vec::with_capacity(eithers.len() - n_lefts);
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for elt in eithers.move_iter() {
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match elt {
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Left(l) => lefts.push(l),
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Right(r) => rights.push(r)
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}
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}
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return (lefts, rights);
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use option::{IntoOption, ToOption, AsOption};
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use option;
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use result::{IntoResult, ToResult, AsResult};
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use result;
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#[test]
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fn test_either_left() {
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let val = Left(10);
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fn f_left(x: &int) -> bool { *x == 10 }
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fn f_right(_x: &uint) -> bool { false }
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assert!(val.either(f_left, f_right));
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}
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#[test]
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fn test_either_right() {
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let val = Right(10u);
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fn f_left(_x: &int) -> bool { false }
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fn f_right(x: &uint) -> bool { *x == 10u }
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assert!(val.either(f_left, f_right));
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}
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#[test]
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fn test_lefts() {
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let input = ~[Left(10), Right(11), Left(12), Right(13), Left(14)];
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let result = lefts(input.move_iter()).to_owned_vec();
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assert_eq!(result, ~[10, 12, 14]);
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}
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#[test]
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fn test_lefts_none() {
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let input: ~[Either<int, int>] = ~[Right(10), Right(10)];
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let result = lefts(input.move_iter()).to_owned_vec();
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assert_eq!(result.len(), 0u);
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}
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#[test]
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fn test_lefts_empty() {
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let input: ~[Either<int, int>] = ~[];
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let result = lefts(input.move_iter()).to_owned_vec();
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assert_eq!(result.len(), 0u);
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}
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#[test]
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fn test_rights() {
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let input = ~[Left(10), Right(11), Left(12), Right(13), Left(14)];
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let result = rights(input.move_iter()).to_owned_vec();
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assert_eq!(result, ~[11, 13]);
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}
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#[test]
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fn test_rights_none() {
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let input: ~[Either<int, int>] = ~[Left(10), Left(10)];
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let result = rights(input.move_iter()).to_owned_vec();
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assert_eq!(result.len(), 0u);
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}
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#[test]
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fn test_rights_empty() {
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let input: ~[Either<int, int>] = ~[];
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let result = rights(input.move_iter()).to_owned_vec();
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assert_eq!(result.len(), 0u);
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}
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#[test]
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fn test_partition() {
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let input = ~[Left(10), Right(11), Left(12), Right(13), Left(14)];
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let (lefts, rights) = partition(input);
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assert_eq!(lefts[0], 10);
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assert_eq!(lefts[1], 12);
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assert_eq!(lefts[2], 14);
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assert_eq!(rights[0], 11);
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assert_eq!(rights[1], 13);
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}
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#[test]
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fn test_partition_no_lefts() {
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let input: ~[Either<int, int>] = ~[Right(10), Right(11)];
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let (lefts, rights) = partition(input);
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assert_eq!(lefts.len(), 0u);
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assert_eq!(rights.len(), 2u);
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}
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#[test]
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fn test_partition_no_rights() {
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let input: ~[Either<int, int>] = ~[Left(10), Left(11)];
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let (lefts, rights) = partition(input);
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assert_eq!(lefts.len(), 2u);
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assert_eq!(rights.len(), 0u);
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}
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#[test]
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fn test_partition_empty() {
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let input: ~[Either<int, int>] = ~[];
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let (lefts, rights) = partition(input);
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assert_eq!(lefts.len(), 0u);
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assert_eq!(rights.len(), 0u);
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}
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#[test]
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pub fn test_to_option() {
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let right: Either<int, int> = Right(100);
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let left: Either<int, int> = Left(404);
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assert_eq!(right.to_option(), option::Some(100));
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assert_eq!(left.to_option(), option::None);
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}
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#[test]
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pub fn test_into_option() {
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let right: Either<int, int> = Right(100);
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let left: Either<int, int> = Left(404);
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assert_eq!(right.into_option(), option::Some(100));
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assert_eq!(left.into_option(), option::None);
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}
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#[test]
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pub fn test_as_option() {
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let right: Either<int, int> = Right(100);
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let left: Either<int, int> = Left(404);
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assert_eq!(right.as_option().unwrap(), &100);
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assert_eq!(left.as_option(), option::None);
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}
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#[test]
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pub fn test_to_result() {
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let right: Either<int, int> = Right(100);
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let left: Either<int, int> = Left(404);
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assert_eq!(right.to_result(), result::Ok(100));
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assert_eq!(left.to_result(), result::Err(404));
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}
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#[test]
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pub fn test_into_result() {
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let right: Either<int, int> = Right(100);
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let left: Either<int, int> = Left(404);
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assert_eq!(right.into_result(), result::Ok(100));
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assert_eq!(left.into_result(), result::Err(404));
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}
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#[test]
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pub fn test_as_result() {
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let right: Either<int, int> = Right(100);
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let left: Either<int, int> = Left(404);
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let x = 100;
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assert_eq!(right.as_result(), result::Ok(&x));
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let x = 404;
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assert_eq!(left.as_result(), result::Err(&x));
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}
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#[test]
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pub fn test_to_either() {
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let right: Either<int, int> = Right(100);
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let left: Either<int, int> = Left(404);
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assert_eq!(right.to_either(), Right(100));
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assert_eq!(left.to_either(), Left(404));
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}
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#[test]
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pub fn test_into_either() {
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let right: Either<int, int> = Right(100);
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let left: Either<int, int> = Left(404);
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assert_eq!(right.into_either(), Right(100));
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assert_eq!(left.into_either(), Left(404));
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}
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#[test]
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pub fn test_as_either() {
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let right: Either<int, int> = Right(100);
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let left: Either<int, int> = Left(404);
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assert_eq!(right.as_either().unwrap_right(), &100);
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assert_eq!(left.as_either().unwrap_left(), &404);
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}
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}
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