rust/src/libextra/list.rs

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// Copyright 2012 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.
//! A standard, garbage-collected linked list.
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#[deriving(Clone, Eq)]
pub enum List<T> {
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Cons(T, @List<T>),
Nil,
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}
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#[deriving(Eq)]
pub enum MutList<T> {
MutCons(T, @mut MutList<T>),
MutNil,
}
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/// Create a list from a vector
pub fn from_vec<T:Clone + 'static>(v: &[T]) -> @List<T> {
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v.rev_iter().fold(@Nil::<T>, |t, h| @Cons((*h).clone(), t))
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}
/**
* Left fold
*
* Applies `f` to `u` and the first element in the list, then applies `f` to
* the result of the previous call and the second element, and so on,
* returning the accumulated result.
*
* # Arguments
*
* * ls - The list to fold
* * z - The initial value
* * f - The function to apply
*/
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pub fn foldl<T:Clone,U>(z: T, ls: @List<U>, f: &fn(&T, &U) -> T) -> T {
let mut accum: T = z;
do iter(ls) |elt| { accum = f(&accum, elt);}
accum
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}
/**
* Search for an element that matches a given predicate
*
* Apply function `f` to each element of `v`, starting from the first.
* When function `f` returns true then an option containing the element
* is returned. If `f` matches no elements then none is returned.
*/
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pub fn find<T:Clone>(ls: @List<T>, f: &fn(&T) -> bool) -> Option<T> {
let mut ls = ls;
loop {
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ls = match *ls {
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Cons(ref hd, tl) => {
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if f(hd) { return Some((*hd).clone()); }
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tl
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}
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Nil => return None
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}
};
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}
/// Returns true if a list contains an element with the given value
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pub fn has<T:Eq>(ls: @List<T>, elt: T) -> bool {
let mut found = false;
do each(ls) |e| {
if *e == elt { found = true; false } else { true }
};
return found;
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}
/// Returns true if the list is empty
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pub fn is_empty<T>(ls: @List<T>) -> bool {
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match *ls {
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Nil => true,
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_ => false
}
}
/// Returns the length of a list
pub fn len<T>(ls: @List<T>) -> uint {
let mut count = 0u;
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iter(ls, |_e| count += 1u);
count
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}
/// Returns all but the first element of a list
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pub fn tail<T>(ls: @List<T>) -> @List<T> {
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match *ls {
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Cons(_, tl) => return tl,
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Nil => fail2!("list empty")
}
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}
/// Returns the first element of a list
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pub fn head<T:Clone>(ls: @List<T>) -> T {
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match *ls {
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Cons(ref hd, _) => (*hd).clone(),
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// makes me sad
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_ => fail2!("head invoked on empty list")
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}
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}
/// Appends one list to another
pub fn append<T:Clone + 'static>(l: @List<T>, m: @List<T>) -> @List<T> {
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match *l {
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Nil => return m,
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Cons(ref x, xs) => {
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let rest = append(xs, m);
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return @Cons((*x).clone(), rest);
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}
}
}
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/*
/// Push one element into the front of a list, returning a new list
/// THIS VERSION DOESN'T ACTUALLY WORK
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fn push<T:Clone>(ll: &mut @list<T>, vv: T) {
ll = &mut @cons(vv, *ll)
}
*/
/// Iterate over a list
pub fn iter<T>(l: @List<T>, f: &fn(&T)) {
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let mut cur = l;
loop {
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cur = match *cur {
Cons(ref hd, tl) => {
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f(hd);
tl
}
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Nil => break
}
}
}
/// Iterate over a list
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pub fn each<T>(l: @List<T>, f: &fn(&T) -> bool) -> bool {
let mut cur = l;
loop {
cur = match *cur {
Cons(ref hd, tl) => {
if !f(hd) { return false; }
tl
}
Nil => { return true; }
}
}
}
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impl<T> MutList<T> {
/// Iterate over a mutable list
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pub fn each(@mut self, f: &fn(&mut T) -> bool) -> bool {
let mut cur = self;
loop {
let borrowed = &mut *cur;
cur = match *borrowed {
MutCons(ref mut hd, tl) => {
if !f(hd) {
return false;
}
tl
}
MutNil => break
}
}
return true;
}
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}
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#[cfg(test)]
mod tests {
use list::*;
use list;
use std::option;
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#[test]
fn test_is_empty() {
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let empty : @list::List<int> = from_vec([]);
let full1 = from_vec([1]);
let full2 = from_vec(['r', 'u']);
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assert!(is_empty(empty));
assert!(!is_empty(full1));
assert!(!is_empty(full2));
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}
#[test]
fn test_from_vec() {
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let l = from_vec([0, 1, 2]);
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assert_eq!(head(l), 0);
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let tail_l = tail(l);
assert_eq!(head(tail_l), 1);
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let tail_tail_l = tail(tail_l);
assert_eq!(head(tail_tail_l), 2);
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}
#[test]
fn test_from_vec_empty() {
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let empty : @list::List<int> = from_vec([]);
assert_eq!(empty, @list::Nil::<int>);
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}
#[test]
fn test_foldl() {
fn add(a: &uint, b: &int) -> uint { return *a + (*b as uint); }
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let l = from_vec([0, 1, 2, 3, 4]);
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let empty = @list::Nil::<int>;
assert_eq!(list::foldl(0u, l, add), 10u);
assert_eq!(list::foldl(0u, empty, add), 0u);
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}
#[test]
fn test_foldl2() {
fn sub(a: &int, b: &int) -> int {
*a - *b
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}
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let l = from_vec([1, 2, 3, 4]);
assert_eq!(list::foldl(0, l, sub), -10);
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}
#[test]
fn test_find_success() {
fn match_(i: &int) -> bool { return *i == 2; }
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let l = from_vec([0, 1, 2]);
assert_eq!(list::find(l, match_), option::Some(2));
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}
#[test]
fn test_find_fail() {
fn match_(_i: &int) -> bool { return false; }
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let l = from_vec([0, 1, 2]);
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let empty = @list::Nil::<int>;
assert_eq!(list::find(l, match_), option::None::<int>);
assert_eq!(list::find(empty, match_), option::None::<int>);
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}
#[test]
fn test_has() {
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let l = from_vec([5, 8, 6]);
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let empty = @list::Nil::<int>;
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assert!((list::has(l, 5)));
assert!((!list::has(l, 7)));
assert!((list::has(l, 8)));
assert!((!list::has(empty, 5)));
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}
#[test]
fn test_len() {
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let l = from_vec([0, 1, 2]);
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let empty = @list::Nil::<int>;
assert_eq!(list::len(l), 3u);
assert_eq!(list::len(empty), 0u);
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}
#[test]
fn test_append() {
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assert!(from_vec([1,2,3,4])
== list::append(list::from_vec([1,2]), list::from_vec([3,4])));
}
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}