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/*
Module: list
A standard linked list
*/
import core::option;
import option::*;
import option::{some, none};
/* Section: Types */
/*
Tag: list
*/
tag list<T> {
/* Variant: cons */
cons(T, @list<T>);
/* Variant: nil */
nil;
}
/*Section: Operations */
/*
Function: from_vec
Create a list from a vector
*/
fn from_vec<T: copy>(v: [const T]) -> list<T> {
*vec::foldr(v, @nil::<T>, { |h, t| @cons(h, t) })
}
/*
Function: foldl
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.
Parameters:
ls - The list to fold
z - The initial value
f - The function to apply
*/
fn foldl<T: copy, U>(ls: list<U>, z: T, f: block(T, U) -> T) -> T {
let accum: T = z;
iter(ls) {|elt| accum = f(accum, elt);}
accum
}
/*
Function: find
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, U: copy>(ls: list<T>, f: block(T) -> option::t<U>)
-> option::t<U> {
let ls = ls;
while true {
alt ls {
cons(hd, tl) {
alt f(hd) { none. { ls = *tl; } some(rs) { ret some(rs); } }
}
nil. { break; }
}
}
ret none;
}
/*
Function: has
Returns true if a list contains an element with the given value
*/
fn has<T: copy>(ls: list<T>, elt: T) -> bool {
let ls = ls;
while true {
alt ls {
cons(hd, tl) { if elt == hd { ret true; } else { ls = *tl; } }
nil. { break; }
}
}
ret false;
}
/*
Function: is_empty
Returns true if the list is empty.
*/
pure fn is_empty<T: copy>(ls: list<T>) -> bool {
alt ls {
nil. { true }
_ { false }
}
}
/*
Function: is_not_empty
Returns true if the list is not empty.
*/
pure fn is_not_empty<T: copy>(ls: list<T>) -> bool {
ret !is_empty(ls);
}
/*
Function: len
Returns the length of a list
*/
fn len<T>(ls: list<T>) -> uint {
let count = 0u;
iter(ls) {|_e| count += 1u;}
count
}
/*
Function: tail
Returns all but the first element of a list
*/
pure fn tail<T: copy>(ls: list<T>) : is_not_empty(ls) -> list<T> {
alt ls {
cons(_, tl) { ret *tl; }
nil. { fail "list empty" }
}
}
/*
Function: head
Returns the first element of a list
*/
pure fn head<T: copy>(ls: list<T>) : is_not_empty(ls) -> T {
alt ls {
cons(hd, _) { ret hd; }
nil. { fail "list empty" }
}
}
/*
Function: append
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); }
}
}
/*
Function: iter
Iterate over a list
*/
fn iter<T>(l: list<T>, f: block(T)) {
alt l {
cons(hd, tl) {
f(hd);
let cur = tl;
while true {
alt *cur {
cons(hd, tl) {
f(hd);
cur = tl;
}
nil. { break; }
}
}
}
nil. {}
}
}
// Local Variables:
// mode: rust;
// fill-column: 78;
// indent-tabs-mode: nil
// c-basic-offset: 4
// buffer-file-coding-system: utf-8-unix
// End:
|
