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/////////////////////////////////////////////////////////////////////////// | |
// The iterator trait | |
trait MutIterator<T> { | |
fn has_next(&self) -> bool; | |
fn next<'a>(&'a mut self) -> &'a mut T; | |
} | |
/////////////////////////////////////////////////////////////////////////// | |
// Implementation for vectors (easy) | |
struct MutSliceIterator<'self, T> { | |
v: &'self mut [T], | |
pos: uint, | |
} | |
impl<'self, T> MutIterator<T> for MutSliceIterator<'self, T> { | |
fn has_next(&self) -> bool { | |
self.pos == self.v.len() | |
} | |
fn next<'a>(&'a mut self) -> &'a mut T { | |
if self.pos == self.v.len() { | |
fail!("next() called when has_next() is false"); | |
} | |
let p = self.pos; | |
self.pos += 1; | |
&mut self.v[p] | |
} | |
} | |
////////////////////////////////////////////// | |
// Implementation for a binary tree (pre-order, trickier) | |
struct BinaryTree<T> { | |
value: T, | |
left: Option<~BinaryTree<T>>, | |
right: Option<~BinaryTree<T>>, | |
} | |
impl<T> BinaryTree<T> { | |
fn iterator<'a>(&'a mut self) -> BinaryTreePreorderMutIterator<'a, T> { | |
BinaryTreePreorderMutIterator { | |
stack: ~[self] | |
} | |
} | |
} | |
struct BinaryTreePreorderMutIterator<'self,T> { | |
stack: ~[&'self mut BinaryTree<T>], | |
} | |
impl<'self,T> MutIterator<T> for BinaryTreePreorderMutIterator<'self,T> { | |
fn has_next(&self) -> bool { | |
!self.stack.is_empty() | |
} | |
fn next<'a>(&'a mut self) -> &'a mut T { | |
if !self.has_next() { | |
fail!("next() called when has_next() is false"); | |
} | |
let cur = self.stack.pop(); | |
match cur.right { | |
None => {} | |
Some(~ref mut r) => { | |
self.stack.push(r); | |
} | |
} | |
match cur.left { | |
None => {} | |
Some(~ref mut l) => { | |
self.stack.push(l); | |
} | |
} | |
&mut cur.value | |
} | |
} | |
#[cfg(test)] | |
fn check_iter<V:Eq>(mut iter: BinaryTreePreorderMutIterator<V>, | |
values: &[V]) { | |
let mut counter = 0_u; | |
while iter.has_next() { | |
let next = iter.next(); | |
if *next != values[counter] { | |
fail!(fmt!("Index %u yielded %? not %?", | |
counter, *next, values[counter])); | |
} | |
counter += 1_u; | |
} | |
assert_eq!(counter, values.len()); | |
} | |
#[test] | |
pub fn preorder1() { | |
let mut the_tree = BinaryTree { | |
value: "r", | |
left: Some(~BinaryTree { | |
value: "r.l", | |
left: None, | |
right: Some(~BinaryTree { | |
value: "r.l.r", | |
left: None, | |
right: None | |
}), | |
}), | |
right: Some(~BinaryTree { | |
value: "r.r", | |
left: Some(~BinaryTree { | |
value: "r.r.l", | |
left: None, | |
right: None, | |
}), | |
right: Some(~BinaryTree { | |
value: "r.r.r", | |
left: None, | |
right: None | |
}), | |
}), | |
}; | |
check_iter(the_tree.iterator(), | |
["r", "r.l", "r.l.r", "r.r", "r.r.l", "r.r.r"]); | |
} | |
fn main() {} |
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