//! A standard linked list import core::option; import option::*; import option::{some, none}; enum list { cons(T, @list), nil, } /// Create a list from a vector fn from_vec(v: &[T]) -> @list { vec::foldr(v, @nil::, |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(z: T, ls: @list, 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(ls: @list, f: fn(T) -> bool) -> option { 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(ls: @list, 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(ls: @list) -> bool { alt *ls { nil { true } _ { false } } } /// Returns true if the list is not empty pure fn is_not_empty(ls: @list) -> bool { ret !is_empty(ls); } /// Returns the length of a list fn len(ls: @list) -> uint { let mut count = 0u; iter(ls, |_e| count += 1u); count } /// Returns all but the first element of a list pure fn tail(ls: @list) -> @list { alt *ls { cons(_, tl) { ret tl; } nil { fail ~"list empty" } } } /// Returns the first element of a list pure fn head(ls: @list) -> T { alt check *ls { cons(hd, _) { hd } } } /// Appends one list to another pure fn append(l: @list, m: @list) -> @list { 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(&l: list, v: T) { l = cons(v, @l); } /// Iterate over a list fn iter(l: @list, 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(l: @list, 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 = 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 = from_vec(~[]); assert (empty == @list::nil::); } #[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::; 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::; assert (list::find(l, match_) == option::none::); assert (list::find(empty, match_) == option::none::); } #[test] fn test_has() { let l = from_vec(~[5, 8, 6]); let empty = @list::nil::; 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::; 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: