Visit the free functions of std::vec and reimplement or remove some. Most prominently, remove `each_permutation` and replace with two iterators, ElementSwaps and Permutations.
Replace unzip, unzip_slice with an updated `unzip` that works with an iterator argument.
Replace each_permutation with a Permutation iterator. The new permutation iterator is more efficient since it uses an algorithm that produces permutations in an order where each is only one element swap apart, including swapping back to the original state with one swap at the end.
Unify the seldomly used functions `build`, `build_sized`, `build_sized_opt` into just one function `build`.
Remove `equal_sizes`
I've reversed my thinking on this restrictive definition of eq after
two separate bugs were hidden by commenting it out; it's better to
get ICEs than SIGSEGV's, any day.
RE-ENABLING ICE MACHINE!
These functions have very few users since they are mostly replaced by
iterator-based constructions.
Convert a few remaining users in-tree, and reduce the number of
functions by basically renaming build_sized_opt to build, and removing
the other two. This for both the vec and the at_vec versions.
The basic construct x.len() == y.len() is just as simple.
This function used to be a precondition (not sure about the
terminology), so it had to be a function. This is not relevant any more.
Update for a lot of changes (not many free functions left), add examples
of the important methods `slice` and `push`, and write a short bit about
iteration.
Introduce ElementSwaps and Permutations. ElementSwaps is an iterator
that for a given sequence length yields the element swaps needed
to visit each possible permutation of the sequence in turn.
We use an algorithm that generates a sequence such that each permutation
is only one swap apart.
let mut v = [1, 2, 3];
for perm in v.permutations_iter() {
// yields 1 2 3 | 1 3 2 | 3 1 2 | 3 2 1 | 2 3 1 | 2 1 3
}
The `.permutations_iter()` yields clones of the input vector for each
permutation.
If a copyless traversal is needed, it can be constructed with
`ElementSwaps`:
for (a, b) in ElementSwaps::new(3) {
// yields (2, 1), (1, 0), (2, 1) ...
v.swap(a, b);
// ..
}
The trait will keep the `Iterator` naming, but a more concise module
name makes using the free functions less verbose. The module will define
iterables in addition to iterators, as it deals with iteration in
general.
The trait will keep the `Iterator` naming, but a more concise module
name makes using the free functions less verbose. The module will define
iterables in addition to iterators, as it deals with iteration in
general.
This removes another large chunk of this odd 'clownshoes' identifier showing up
in symbol names. These all originated from external crates because the encoded
items were encoded independently of the paths calculated in ast_map. The
encoding of these paths now uses the helper function in ast_map to calculate the
"pretty name" for an impl block.
Unfortunately there is still no information about generics in the symbol name,
but it's certainly vastly better than before
hash::__extensions__::write::_version::v0.8
becomes
hash::Writer$SipState::write::hversion::v0.8
This also fixes bugs in which lots of methods would show up as `meth_XXX`, they
now only show up as `meth` and throw some extra characters onto the version
string.
Here are fixes for more problems mentioned in #8787. I think I've addressed everything mentioned there except for @nikomatsakis's comment about match/patterns now. (This also fixes the bug in struct alignment that @pnkfelix mentioned from my earlier pull request #8872.)
The biggest change here is to make fill-paragraph (M-q) and auto-fill-mode work inside different variations of multi-line and doc comments. Because of the way emacs paragraph fills work (callbacks interacting with global regexp variables that are used in odd ways) there were quite a few edge cases that I had to work around.
The only way I was able to keep it all straight was to create some regression tests. They use the emacs lisp regression testing tool ERT, and are included as the last commit here. I added a few tests for indentation as well. I have not attempted to integrate the tests into the overall rust compiler build process, since I can't imagine anyone would want the compiler build to have a dependency on emacs. Maybe at some point tools like this get their own repositories? Just a thought.
One other thought related to the tests: should there be a place to put these types of style samples that isn't specific to one text editor? Maybe as part of an official rust style guide, but in a form that would allow tools like this to pull out the samples and use them for tests?
This is a patch to fix#6031. I didn't see any tests for the C++ library code, so I didn't write a test for my changes. Did I miss something, or are there really no tests?
This allows cross-crate inlining which is *very* good because this is called a
lot throughout libstd (even when libstd is inlined across crates).
In one of my projects, I have a test case with the following performance characteristics
commit | optimization level | runtime (seconds)
----|------|----
before | O2 | 22s
before | O3 | 107s
after | O2 | 13s
after | O3 | 12s
I'm a bit disturbed by the 107s runtime from O3 before this commit. The performance characteristics of this test involve doing an absurd amount of small operations. A huge portion of this is creating hashmaps which involves allocating vectors.
The worst portions of the profile are:
Which as you can see looks like some *serious* problems with inlining. I would expect the hash map methods to be high up in the profile, but the top 9 callers of `cast::transmute_copy` were `Repr::repr`'s various monomorphized instances.
I wish there we a better way to detect things like this in the future, and it's unfortunate that this is required for performance in the first place. I suppose I'm not entirely sure why this is needed because all of the methods should have been generated in-crate (monomorphized versions of library functions), so they should have gotten inlined? It also could just be that by modifying LLVM's idea of the inline cost of this function it was able to inline it in many more locations.
This removes another large chunk of this odd 'clownshoes' identifier showing up
in symbol names. These all originated from external crates because the encoded
items were encoded independently of the paths calculated in ast_map. The
encoding of these paths now uses the helper function in ast_map to calculate the
"pretty name" for an impl block.
Unfortunately there is still no information about generics in the symbol name,
but it's certainly vastly better than before
hash::__extensions__::write::_version::v0.8
becomes
hash::Writer$SipState::write::hversion::v0.8
This also fixes bugs in which lots of methods would show up as `meth_XXX`, they
now only show up as `meth` and throw some extra characters onto the version
string.
The ISO 8601 standard does not mandate any specific precision for
fractional seconds, so this accepts input of any length, ignoring the
part after the nanoseconds place. It may be more correct to round with
the tenths of nanoseconds digit, but then we'd have to deal with
carrying the round through the entire Tm struct (e.g. for a time like
Dec 31 11:59.999999999999).
%f is the format specifier that Python's datetime library uses for
0-padded microseconds so it seemed appropriate here.
cc #2350
bors
