Oh, one other thing:
Your each() method does not obey the for protocol! When the callback
returns false, you should abort iteration altogether. This presumably
means you need to do the recursion in a helper method that itself
returns bool so that you can detect when to carry on and when to abort.
Niko
Steve Jenson wrote:
On Thu, Dec 27, 2012 at 3:16 PM, Niko Matsakis <[email protected]
<mailto:[email protected]>> wrote:
I'm sorry for not replying more quickly, I was not checking e-mail
over xmas break. I do not know of any general problems with @ and
borrowing. In any event, this is a misdiagnosis.
No problem with reply timing.
The problem is this: the declaration of iter looks like this:
impl<K: Copy Eq Ord, V: Copy> RBMap<K, V>: iter::BaseIter<(&K,
&V)>
In the context of a type declaration, an & means `&self`, where
`self` is the lifetime parameter associated with the
type/impl/whatever (just as the impl has two type parameters K and
V, it also has an implicit lifetime parameter `self`). So, this
declaration written out more explicitly would be:
impl<K: Copy Eq Ord, V: Copy> RBMap<K, V>:
iter::BaseIter<(&self/K, &self/V)>
However, your method declaration is:
pure fn each(&self, f: fn(&(&K, &V)) -> bool) { ... }
In the context of a function declaration, & means "a fresh
lifetime". So this winds up being short for a declaration life this:
pure fn each(&self, f: fn(&a/(&a/K, &a/V)) -> bool) { ... }
However, the trait declares that `each` should have this type:
pure fn each(&self, f: fn(&a/(&self/K, &self/V)) -> bool) { ... }
So I think that if you change your declaraiton of `each()` to:
pure fn each(&self, f: fn(&(&self/K, &self/V)) -> bool) { ... }
It will work just fine. I apologize for the cryptic error
message. Working on it.
Unfortunately not but a much more interesting set of error messages
about lifetimes is coming out now: http://pastebin.com/SYwCw1ac
And here is a link to the each method again (I pushed this broken
version to github so I can share the exact changes I made)
https://github.com/stevej/rustled/blob/master/red_black_tree.rs#L96
Thanks a bunch for all of your clarifying comments and blog posts.
Steve
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