rust/src/libstd/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 linked list
#[forbid(deprecated_mode)];
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use core::cmp::Eq;
use core::option;
use option::*;
use option::{Some, None};
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#[deriving_eq]
pub enum List<T> {
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Cons(T, @List<T>),
Nil,
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}
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/// Cregate a list from a vector
pub fn from_vec<T: Copy>(v: &[T]) -> @List<T> {
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vec::foldr(v, @Nil::<T>, |h, t| @Cons(*h, 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
*/
pub fn foldl<T: Copy, 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.
*/
pub fn find<T: Copy>(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) => {
if f(hd) { return Some(*hd); }
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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
pub fn has<T: Copy Eq>(ls: @List<T>, elt: T) -> bool {
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for each(ls) |e| {
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if *e == elt { return true; }
}
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return false;
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}
/// Returns true if the list is empty
pub pure fn is_empty<T: Copy>(ls: @List<T>) -> bool {
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match *ls {
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Nil => true,
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_ => false
}
}
/// Returns true if the list is not empty
pub pure fn is_not_empty<T: Copy>(ls: @List<T>) -> bool {
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return !is_empty(ls);
}
/// 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
pub pure fn tail<T: Copy>(ls: @List<T>) -> @List<T> {
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match *ls {
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Cons(_, tl) => return tl,
Nil => fail ~"list empty"
}
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}
/// Returns the first element of a list
pub pure fn head<T: Copy>(ls: @List<T>) -> T {
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match *ls {
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Cons(copy hd, _) => hd,
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// makes me sad
_ => fail ~"head invoked on empty list"
}
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}
/// Appends one list to another
pub pure fn append<T: Copy>(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(copy x, xs) => {
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let rest = append(xs, m);
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return @Cons(x, 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
pure fn push<T: Copy>(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
pub fn each<T>(l: @List<T>, f: fn(&T) -> bool) {
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let mut cur = l;
loop {
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cur = match *cur {
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Cons(ref hd, tl) => {
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if !f(hd) { return; }
tl
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}
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Nil => break
}
}
}
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#[cfg(test)]
mod tests {
#[legacy_exports];
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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);
assert !is_not_empty(empty);
assert is_not_empty(full1);
assert is_not_empty(full2);
}
#[test]
fn test_from_vec() {
let l = from_vec(~[0, 1, 2]);
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assert (head(l) == 0);
let tail_l = tail(l);
assert (head(tail_l) == 1);
let tail_tail_l = tail(tail_l);
assert (head(tail_tail_l) == 2);
}
#[test]
fn test_from_vec_empty() {
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let empty : @list::List<int> = from_vec(~[]);
assert (empty == @list::Nil::<int>);
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}
#[test]
fn test_foldl() {
fn add(a: &uint, b: &int) -> uint { return *a + (*b as uint); }
let l = from_vec(~[0, 1, 2, 3, 4]);
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let empty = @list::Nil::<int>;
assert (list::foldl(0u, l, add) == 10u);
assert (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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}
let l = from_vec(~[1, 2, 3, 4]);
assert (list::foldl(0, l, sub) == -10);
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}
#[test]
fn test_find_success() {
fn match_(i: &int) -> bool { return *i == 2; }
let l = from_vec(~[0, 1, 2]);
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assert (list::find(l, match_) == option::Some(2));
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}
#[test]
fn test_find_fail() {
fn match_(_i: &int) -> bool { return false; }
let l = from_vec(~[0, 1, 2]);
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let empty = @list::Nil::<int>;
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assert (list::find(l, match_) == option::None::<int>);
assert (list::find(empty, match_) == option::None::<int>);
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}
#[test]
fn test_has() {
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));
}
#[test]
fn test_len() {
let l = from_vec(~[0, 1, 2]);
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let empty = @list::Nil::<int>;
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assert (list::len(l) == 3u);
assert (list::len(empty) == 0u);
}
#[test]
fn test_append() {
assert from_vec(~[1,2,3,4])
== list::append(list::from_vec(~[1,2]), list::from_vec(~[3,4]));
}
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}
// Local Variables:
// mode: rust;
// fill-column: 78;
// indent-tabs-mode: nil
// c-basic-offset: 4
// buffer-file-coding-system: utf-8-unix
// End: