This is an implementation of a map and set for integer keys. It's an ordered container (by byte order, which is sorted order for integers and byte strings when done in the right direction) with O(1) worst-case lookup, removal and insertion. There's no rebalancing or rehashing so it's actually O(1) without amortizing any costs.
The fanout can be adjusted in multiples of 2 from 2-ary through 256-ary, but it's hardcoded at 16-ary because there isn't a way to expose that in the type system yet. To keep things simple, it also only allows `uint` keys, but later I'll expand it to all the built-in integer types and byte arrays.
There's quite a bit of room for performance improvement, along with the boost that will come with dropping the headers on `Owned` `~` and getting rid of the overhead from the stack switches to the allocator. It currently does suffix compression for a single node and then splits into two n-ary trie nodes, which could be replaced with an array for at least 4-8 suffixes before splitting it. There's also the option of doing path compression, which may be a good or a bad idea and depends a lot on the data stored.
I want to share the test suite with the other maps so that's why I haven't duplicated all of the existing integer key tests in this file. I'll send in another pull request to deal with that.
Current benchmark numbers against the other map types:
TreeMap:
Sequential integers:
insert: 0.798295
search: 0.188931
remove: 0.435923
Random integers:
insert: 1.557661
search: 0.758325
remove: 1.720527
LinearMap:
Sequential integers:
insert: 0.272338
search: 0.141179
remove: 0.190273
Random integers:
insert: 0.293588
search: 0.162677
remove: 0.206142
TrieMap:
Sequential integers:
insert: 0.0901
search: 0.012223
remove: 0.084139
Random integers:
insert: 0.392719
search: 0.261632
remove: 0.470401
@graydon is using an earlier version of this for the garbage collection implementation, so that's why I added this to libcore. I left out the `next` and `prev` methods *for now* because I just wanted the essentials first.
This allows `TreeMap`/`TreeSet` to fully express their requirements and reduces the comparisons from ~1.5 per level to 1 which really helps for string keys.
I also added `ReverseIter` to the prelude exports because I forgot when I originally added it.
The fix is straight-forward, but there are several changes
while fixing the issue.
1) disallow `mut` keyword when making a new struct
In code base, there are following code,
```rust
struct Foo { mut a: int };
let a = Foo { mut a: 1 };
```
This is because of structural record, which is
deprecated corrently (see issue #3089) In structural
record, `mut` keyword should be allowd to control
mutability. But without structural record, we don't
need to allow `mut` keyword while constructing struct.
2) disallow structural records in parser level
This is related to 1). With structural records, there
is an ambiguity between empty block and empty struct
To solve the problem, I change parser to stop parsing
structural records. I think this is not a problem,
because structural records are not compiled already.
Misc. issues
There is an ambiguity between empty struct vs. empty match stmt.
with following code,
```rust
match x{} {}
```
Two interpretation is possible, which is listed blow
```rust
match (x{}) {} // matching with newly-constructed empty struct
(match x{}) {} // matching with empty enum(or struct) x
// and then empty block
```
It seems that there is no such code in rust code base, but
there is one test which uses empty match statement:
https://github.com/mozilla/rust/blob/incoming/src/test/run-pass/issue-3037.rs
All other cases could be distinguished with look-ahead,
but this can't be. One possible solution is wrapping with
parentheses when matching with an uninhabited type.
```rust
enum what { }
fn match_with_empty(x: what) -> ~str {
match (x) { //use parentheses to remove the ambiguity
}
}
```
r?
This fixes the current [random failures](http://buildbot.rust-lang.org/builders/auto-linux/builds/291/steps/test/logs/stdio) on the bots and closes#4436 by removing `unwrap_shared_mutable_state` and the code that depends on it. The result is that ARC-like things will not be unwrappable. This feature is complex and is not used outside of test cases.
Note that there is not consensus to remove it.
(second commit)
This removes all but 6 uses of `drop {}` from the entire codebase. Removing any of the remaining uses causes various non-trivial bugs; I'll start reporting them once this gets merged.
See issue #4869. I'm not quite sure what constitutes "consensus from the core team" (cf. discussion in the issue), but this at least demonstrates that the proposed change is pretty straightforward.
After this change, there are no new test failures. I've un-ignored the `to_str` vectors test; it's not at all obvious to me why it'd be problematic, and it passes on my Linux machine.
r?
#3406
Pretty straightforward. I'm using opaque pointers instead trying to get trans and core to agree on the types of the main function and crate map. One oddity is that this required changing the order of the `-lrustrt` argument to the linker in order to resolve `upcall_new_stack`. Linkers are mysterious.
r?
After this patch, macros declared in a module, function, or block can only be used inside of that module, function or block, with the exception of modules declared with the #[macro_escape] attribute; these modules allow macros to escape, and can be used as a limited macro export mechanism.
This pull request also includes miscellaneous comments, lots of new test cases, a few renamings, and a few as-yet-unused data definitions for hygiene.
