1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
|
//! A standard linked list
import core::option;
import option::*;
import option::{some, none};
enum list<T> {
cons(T, @list<T>),
nil,
}
/// Create a list from a vector
fn from_vec<T: copy>(v: &[T]) -> @list<T> {
vec::foldr(v, @nil::<T>, |h, t| @cons(h, t))
}
/**
* 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
*/
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
}
/**
* 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.
*/
fn find<T: copy>(ls: @list<T>, f: fn(T) -> bool) -> option<T> {
let mut ls = ls;
loop {
ls = alt *ls {
cons(hd, tl) {
if f(hd) { ret some(hd); }
tl
}
nil { ret none; }
}
};
}
/// Returns true if a list contains an element with the given value
fn has<T: copy>(ls: @list<T>, elt: T) -> bool {
for each(ls) |e| {
if e == elt { ret true; }
}
ret false;
}
/// Returns true if the list is empty
pure fn is_empty<T: copy>(ls: @list<T>) -> bool {
alt *ls {
nil { true }
_ { false }
}
}
/// Returns true if the list is not empty
pure fn is_not_empty<T: copy>(ls: @list<T>) -> bool {
ret !is_empty(ls);
}
/// Returns the length of a list
fn len<T>(ls: @list<T>) -> uint {
let mut count = 0u;
iter(ls, |_e| count += 1u);
count
}
/// Returns all but the first element of a list
pure fn tail<T: copy>(ls: @list<T>) -> @list<T> {
alt *ls {
cons(_, tl) { ret tl; }
nil { fail "list empty" }
}
}
/// Returns the first element of a list
pure fn head<T: copy>(ls: @list<T>) -> T {
alt check *ls { cons(hd, _) { hd } }
}
/// Appends one list to another
pure fn append<T: copy>(l: @list<T>, m: @list<T>) -> @list<T> {
alt *l {
nil { ret m; }
cons(x, xs) { let rest = append(xs, m); ret @cons(x, rest); }
}
}
/// Push an element to the front of a list
fn push<T: copy>(&l: list<T>, v: T) {
l = cons(v, @l);
}
/// Iterate over a list
fn iter<T>(l: @list<T>, f: fn(T)) {
let mut cur = l;
loop {
cur = alt *cur {
cons(hd, tl) {
f(hd);
tl
}
nil { break; }
}
}
}
/// Iterate over a list
fn each<T>(l: @list<T>, f: fn(T) -> bool) {
let mut cur = l;
loop {
cur = alt *cur {
cons(hd, tl) {
if !f(hd) { ret; }
tl
}
nil { break; }
}
}
}
#[cfg(test)]
mod tests {
#[test]
fn test_is_empty() {
let empty : @list::list<int> = from_vec(~[]);
let full1 = from_vec(~[1]);
let full2 = from_vec(~['r', 'u']);
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]);
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() {
let empty : @list::list<int> = from_vec(~[]);
assert (empty == @list::nil::<int>);
}
#[test]
fn test_foldl() {
fn add(&&a: uint, &&b: int) -> uint { ret a + (b as uint); }
let l = from_vec(~[0, 1, 2, 3, 4]);
let empty = @list::nil::<int>;
assert (list::foldl(0u, l, add) == 10u);
assert (list::foldl(0u, empty, add) == 0u);
}
#[test]
fn test_foldl2() {
fn sub(&&a: int, &&b: int) -> int {
a - b
}
let l = from_vec(~[1, 2, 3, 4]);
assert (list::foldl(0, l, sub) == -10);
}
#[test]
fn test_find_success() {
fn match(&&i: int) -> bool { ret i == 2; }
let l = from_vec(~[0, 1, 2]);
assert (list::find(l, match) == option::some(2));
}
#[test]
fn test_find_fail() {
fn match(&&_i: int) -> bool { ret false; }
let l = from_vec(~[0, 1, 2]);
let empty = @list::nil::<int>;
assert (list::find(l, match) == option::none::<int>);
assert (list::find(empty, match) == option::none::<int>);
}
#[test]
fn test_has() {
let l = from_vec(~[5, 8, 6]);
let empty = @list::nil::<int>;
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]);
let empty = @list::nil::<int>;
assert (list::len(l) == 3u);
assert (list::len(empty) == 0u);
}
}
// Local Variables:
// mode: rust;
// fill-column: 78;
// indent-tabs-mode: nil
// c-basic-offset: 4
// buffer-file-coding-system: utf-8-unix
// End:
|
