164 lines
3.0 KiB
Rust
164 lines
3.0 KiB
Rust
/*
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Module: list
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A standard linked list
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*/
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import core::option;
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import option::*;
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import option::{some, none};
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/* Section: Types */
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/*
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Tag: list
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*/
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tag list<T> {
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/* Variant: cons */
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cons(T, @list<T>);
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/* Variant: nil */
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nil;
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}
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/*Section: Operations */
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/*
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Function: from_vec
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Create a list from a vector
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*/
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fn from_vec<copy T>(v: [const 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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Function: foldl
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Left fold
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Applies `f` to `u` and the first element in the list, then applies
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`f` to the result of the previous call and the second element,
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and so on, returning the accumulated result.
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Parameters:
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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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fn foldl<copy T, copy U>(ls: list<U>, z: T, f: block(T, U) -> T) -> T {
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let accum: T = z;
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let ls = ls;
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while true {
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alt ls {
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cons(hd, tl) { accum = f(accum, hd); ls = *tl; }
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nil. { break; }
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}
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}
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ret accum;
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}
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/*
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Function: find
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Search for an element that matches a given predicate
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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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fn find<copy T, copy U>(ls: list<T>, f: block(T) -> option::t<U>)
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-> option::t<U> {
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let ls = ls;
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while true {
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alt ls {
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cons(hd, tl) {
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alt f(hd) { none. { ls = *tl; } some(rs) { ret some(rs); } }
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}
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nil. { break; }
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}
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}
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ret none;
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}
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/*
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Function: has
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Returns true if a list contains an element with the given value
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*/
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fn has<copy T>(ls: list<T>, elt: T) -> bool {
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let ls = ls;
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while true {
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alt ls {
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cons(hd, tl) { if elt == hd { ret true; } else { ls = *tl; } }
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nil. { break; }
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}
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}
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ret false;
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}
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/*
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Function: len
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Returns the length of a list
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*/
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fn len<copy T>(ls: list<T>) -> uint {
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fn count<T>(&&u: uint, _t: T) -> uint { ret u + 1u; }
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ret foldl(ls, 0u, bind count(_, _));
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}
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/*
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Function: tail
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Returns all but the first element of a list
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*/
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fn tail<copy T>(ls: list<T>) -> list<T> {
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alt ls { cons(_, tl) { ret *tl; } nil. { fail "list empty" } }
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}
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/*
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Function: head
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Returns the first element of a list
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*/
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fn head<copy T>(ls: list<T>) -> T {
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alt ls { cons(hd, _) { ret hd; } nil. { fail "list empty" } }
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}
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/*
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Function: append
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Appends one list to another
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*/
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fn append<copy T>(l: list<T>, m: list<T>) -> list<T> {
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alt l {
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nil. { ret m; }
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cons(x, xs) { let rest = append(*xs, m); ret cons(x, @rest); }
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}
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}
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/*
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Function: iter
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Iterate over a list
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*/
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fn iter<copy T>(l: list<T>, f: block(T)) {
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let cur = l;
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while cur != nil {
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alt cur {
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cons(hd, tl) {
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f(hd);
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cur = *tl;
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}
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}
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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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