258 lines
6.2 KiB
Rust
258 lines
6.2 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 standard linked list
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use core::cmp::Eq;
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use core::option::*;
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use core::prelude::*;
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use core::vec;
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#[deriving(Eq)]
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pub enum List<T> {
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Cons(T, @List<T>),
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Nil,
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}
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/// Create a list from a vector
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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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}
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/**
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* Left fold
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*
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* Applies `f` to `u` and the first element in the list, then applies `f` to
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* the result of the previous call and the second element, and so on,
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* returning the accumulated result.
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*
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* # Arguments
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*
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* * ls - The list to fold
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* * z - The initial value
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* * f - The function to apply
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*/
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pub fn foldl<T:Copy,U>(z: T, ls: @List<U>, f: &fn(&T, &U) -> T) -> T {
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let mut accum: T = z;
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do iter(ls) |elt| { accum = f(&accum, elt);}
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accum
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}
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/**
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* Search for an element that matches a given predicate
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*
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* Apply function `f` to each element of `v`, starting from the first.
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* When function `f` returns true then an option containing the element
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* is returned. If `f` matches no elements then none is returned.
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*/
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pub fn find<T:Copy>(ls: @List<T>, f: &fn(&T) -> bool) -> Option<T> {
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let mut ls = ls;
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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); }
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tl
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}
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Nil => return None
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}
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};
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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: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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}
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return false;
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}
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/// Returns true if the list is empty
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pub 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
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}
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}
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/// Returns the length of a list
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pub fn len<T>(ls: @List<T>) -> uint {
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let mut count = 0u;
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iter(ls, |_e| count += 1u);
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count
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}
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/// Returns all but the first element of a list
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pub fn tail<T:Copy>(ls: @List<T>) -> @List<T> {
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match *ls {
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Cons(_, tl) => return tl,
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Nil => fail!(~"list empty")
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}
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}
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/// Returns the first element of a list
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pub 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
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_ => fail!(~"head invoked on empty list")
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}
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}
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/// Appends one list to another
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pub 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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}
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}
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/*
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/// Push one element into the front of a list, returning a new list
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/// THIS VERSION DOESN'T ACTUALLY WORK
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fn push<T:Copy>(ll: &mut @list<T>, vv: T) {
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ll = &mut @cons(vv, *ll)
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}
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*/
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/// Iterate over a list
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pub fn iter<T>(l: @List<T>, f: &fn(&T)) {
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let mut cur = l;
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loop {
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cur = match *cur {
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Cons(ref hd, tl) => {
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f(hd);
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tl
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}
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Nil => break
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}
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}
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}
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/// Iterate over a list
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pub fn each<T>(l: @List<T>, f: &fn(&T) -> bool) {
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let mut cur = l;
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loop {
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cur = match *cur {
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Cons(ref hd, tl) => {
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if !f(hd) { return; }
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tl
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}
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Nil => break
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}
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}
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}
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#[cfg(test)]
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mod tests {
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use list::*;
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use list;
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use core::option;
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#[test]
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pub fn test_is_empty() {
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let empty : @list::List<int> = from_vec(~[]);
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let full1 = from_vec(~[1]);
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let full2 = from_vec(~['r', 'u']);
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fail_unless!(is_empty(empty));
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fail_unless!(!is_empty(full1));
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fail_unless!(!is_empty(full2));
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}
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#[test]
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pub fn test_from_vec() {
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let l = from_vec(~[0, 1, 2]);
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fail_unless!((head(l) == 0));
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let tail_l = tail(l);
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fail_unless!((head(tail_l) == 1));
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let tail_tail_l = tail(tail_l);
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fail_unless!((head(tail_tail_l) == 2));
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}
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#[test]
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pub fn test_from_vec_empty() {
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let empty : @list::List<int> = from_vec(~[]);
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fail_unless!((empty == @list::Nil::<int>));
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}
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#[test]
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pub fn test_foldl() {
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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>;
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fail_unless!((list::foldl(0u, l, add) == 10u));
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fail_unless!((list::foldl(0u, empty, add) == 0u));
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}
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#[test]
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pub fn test_foldl2() {
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fn sub(a: &int, b: &int) -> int {
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*a - *b
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}
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let l = from_vec(~[1, 2, 3, 4]);
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fail_unless!((list::foldl(0, l, sub) == -10));
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}
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#[test]
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pub fn test_find_success() {
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fn match_(i: &int) -> bool { return *i == 2; }
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let l = from_vec(~[0, 1, 2]);
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fail_unless!((list::find(l, match_) == option::Some(2)));
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}
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#[test]
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pub fn test_find_fail() {
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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>;
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fail_unless!((list::find(l, match_) == option::None::<int>));
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fail_unless!((list::find(empty, match_) == option::None::<int>));
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}
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#[test]
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pub 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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fail_unless!((list::has(l, 5)));
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fail_unless!((!list::has(l, 7)));
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fail_unless!((list::has(l, 8)));
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fail_unless!((!list::has(empty, 5)));
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}
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#[test]
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pub fn test_len() {
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let l = from_vec(~[0, 1, 2]);
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let empty = @list::Nil::<int>;
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fail_unless!((list::len(l) == 3u));
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fail_unless!((list::len(empty) == 0u));
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}
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#[test]
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pub fn test_append() {
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fail_unless!(from_vec(~[1,2,3,4])
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== list::append(list::from_vec(~[1,2]), list::from_vec(~[3,4])));
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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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