276 lines
6.9 KiB
Rust
276 lines
6.9 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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use cmp::Eq;
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use kinds::Copy;
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use result::Result;
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use result;
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use vec;
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/// The either type
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#[deriving_eq]
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pub enum Either<T, U> {
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Left(T),
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Right(U)
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}
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#[inline(always)]
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pub fn either<T, U, V>(f_left: &fn(&T) -> V,
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f_right: &fn(&U) -> V, value: &Either<T, U>) -> V {
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/*!
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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(T) then `f_left` is applied to its contents, if
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* `value` is right(U) then `f_right` is applied to its contents, and the
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* result is returned.
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*/
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match *value {
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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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pub fn lefts<T:Copy,U>(eithers: &[Either<T, U>]) -> ~[T] {
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//! Extracts from a vector of either all the left values
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do vec::build_sized(eithers.len()) |push| {
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for vec::each(eithers) |elt| {
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match *elt {
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Left(ref l) => { push(*l); }
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_ => { /* fallthrough */ }
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}
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}
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}
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}
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pub fn rights<T, U: Copy>(eithers: &[Either<T, U>]) -> ~[U] {
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//! Extracts from a vector of either all the right values
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do vec::build_sized(eithers.len()) |push| {
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for vec::each(eithers) |elt| {
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match *elt {
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Right(ref r) => { push(*r); }
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_ => { /* fallthrough */ }
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}
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}
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}
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}
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pub fn partition<T, U>(eithers: ~[Either<T, U>])
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-> (~[T], ~[U]) {
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/*!
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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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*/
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let mut lefts: ~[T] = ~[];
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let mut rights: ~[U] = ~[];
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do vec::consume(eithers) |_i, elt| {
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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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#[inline(always)]
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pub pure fn flip<T, U>(eith: Either<T, U>) -> Either<U, T> {
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//! Flips between left and right of a given either
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match eith {
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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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#[inline(always)]
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pub pure fn to_result<T, U>(eith: Either<T, U>)
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-> Result<U, T> {
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/*!
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* Converts either::t to a result::t
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*
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* Converts an `either` type to a `result` type, making the "right" choice
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* an ok result, and the "left" choice a fail
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*/
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match eith {
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Right(r) => result::Ok(r),
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Left(l) => result::Err(l)
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}
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}
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#[inline(always)]
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pub pure fn is_left<T, U>(eith: &Either<T, U>) -> bool {
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//! Checks whether the given value is a left
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match *eith { Left(_) => true, _ => false }
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}
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#[inline(always)]
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pub pure fn is_right<T, U>(eith: &Either<T, U>) -> bool {
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//! Checks whether the given value is a right
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match *eith { Right(_) => true, _ => false }
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}
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#[inline(always)]
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pub pure fn unwrap_left<T,U>(eith: Either<T,U>) -> T {
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//! Retrieves the value in the left branch. Fails if the either is Right.
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match eith {
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Left(x) => x,
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Right(_) => fail!(~"either::unwrap_left Right")
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}
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}
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#[inline(always)]
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pub pure fn unwrap_right<T,U>(eith: Either<T,U>) -> U {
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//! Retrieves the value in the right branch. Fails if the either is Left.
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match eith {
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Right(x) => x,
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Left(_) => fail!(~"either::unwrap_right Left")
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}
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}
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pub impl<T, U> Either<T, U> {
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#[inline(always)]
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fn either<V>(&self, f_left: &fn(&T) -> V, f_right: &fn(&U) -> V) -> V {
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either(f_left, f_right, self)
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}
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#[inline(always)]
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fn flip(self) -> Either<U, T> { flip(self) }
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#[inline(always)]
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fn to_result(self) -> Result<U, T> { to_result(self) }
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#[inline(always)]
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fn is_left(&self) -> bool { is_left(self) }
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#[inline(always)]
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fn is_right(&self) -> bool { is_right(self) }
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#[inline(always)]
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fn unwrap_left(self) -> T { unwrap_left(self) }
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#[inline(always)]
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fn unwrap_right(self) -> U { unwrap_right(self) }
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}
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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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fail_unless!((either(f_left, f_right, &val)));
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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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fail_unless!((either(f_left, f_right, &val)));
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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);
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fail_unless!((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);
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fail_unless!((vec::len(result) == 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);
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fail_unless!((vec::len(result) == 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);
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fail_unless!((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);
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fail_unless!((vec::len(result) == 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);
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fail_unless!((vec::len(result) == 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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fail_unless!((lefts[0] == 10));
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fail_unless!((lefts[1] == 12));
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fail_unless!((lefts[2] == 14));
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fail_unless!((rights[0] == 11));
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fail_unless!((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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fail_unless!((vec::len(lefts) == 0u));
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fail_unless!((vec::len(rights) == 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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fail_unless!((vec::len(lefts) == 2u));
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fail_unless!((vec::len(rights) == 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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fail_unless!((vec::len(lefts) == 0u));
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fail_unless!((vec::len(rights) == 0u));
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}
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//
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// Local Variables:
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// mode: rust
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// fill-column: 78;
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// indent-tabs-mode: nil
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// c-basic-offset: 4
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// buffer-file-coding-system: utf-8-unix
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// End:
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//
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