This change is an implementation of [RFC 69][rfc] which adds a third kind of
global to the language, `const`. This global is most similar to what the old
`static` was, and if you're unsure about what to use then you should use a
`const`.
The semantics of these three kinds of globals are:
* A `const` does not represent a memory location, but only a value. Constants
are translated as rvalues, which means that their values are directly inlined
at usage location (similar to a #define in C/C++). Constant values are, well,
constant, and can not be modified. Any "modification" is actually a
modification to a local value on the stack rather than the actual constant
itself.
Almost all values are allowed inside constants, whether they have interior
mutability or not. There are a few minor restrictions listed in the RFC, but
they should in general not come up too often.
* A `static` now always represents a memory location (unconditionally). Any
references to the same `static` are actually a reference to the same memory
location. Only values whose types ascribe to `Sync` are allowed in a `static`.
This restriction is in place because many threads may access a `static`
concurrently. Lifting this restriction (and allowing unsafe access) is a
future extension not implemented at this time.
* A `static mut` continues to always represent a memory location. All references
to a `static mut` continue to be `unsafe`.
This is a large breaking change, and many programs will need to be updated
accordingly. A summary of the breaking changes is:
* Statics may no longer be used in patterns. Statics now always represent a
memory location, which can sometimes be modified. To fix code, repurpose the
matched-on-`static` to a `const`.
static FOO: uint = 4;
match n {
FOO => { /* ... */ }
_ => { /* ... */ }
}
change this code to:
const FOO: uint = 4;
match n {
FOO => { /* ... */ }
_ => { /* ... */ }
}
* Statics may no longer refer to other statics by value. Due to statics being
able to change at runtime, allowing them to reference one another could
possibly lead to confusing semantics. If you are in this situation, use a
constant initializer instead. Note, however, that statics may reference other
statics by address, however.
* Statics may no longer be used in constant expressions, such as array lengths.
This is due to the same restrictions as listed above. Use a `const` instead.
[breaking-change]
Closes#17718
[rfc]: https://github.com/rust-lang/rfcs/pull/246
This uses a bitwise mask to ensure that there's no bounds checking for
the array accesses when generating the next random number. This isn't
costless, but the single instruction is nothing compared to the branch.
A `debug_assert` for "bounds check" is preserved to ensure that
refactoring doesn't accidentally break it (i.e. create values of `cnt`
that are out of bounds with the masking causing it to silently wrap-
around).
Before:
test test::rand_isaac ... bench: 990 ns/iter (+/- 24) = 808 MB/s
test test::rand_isaac64 ... bench: 614 ns/iter (+/- 25) = 1302 MB/s
After:
test test::rand_isaac ... bench: 877 ns/iter (+/- 134) = 912 MB/s
test test::rand_isaac64 ... bench: 470 ns/iter (+/- 30) = 1702 MB/s
(It also removes the unsafe code in Isaac64Rng.next_u64, with a *gain*
in performance; today is a good day.)
declared with the same name in the same scope.
This breaks several common patterns. First are unused imports:
use foo::bar;
use baz::bar;
Change this code to the following:
use baz::bar;
Second, this patch breaks globs that import names that are shadowed by
subsequent imports. For example:
use foo::*; // including `bar`
use baz::bar;
Change this code to remove the glob:
use foo::{boo, quux};
use baz::bar;
Or qualify all uses of `bar`:
use foo::{boo, quux};
use baz;
... baz::bar ...
Finally, this patch breaks code that, at top level, explicitly imports
`std` and doesn't disable the prelude.
extern crate std;
Because the prelude imports `std` implicitly, there is no need to
explicitly import it; just remove such directives.
The old behavior can be opted into via the `import_shadowing` feature
gate. Use of this feature gate is discouraged.
This implements RFC #116.
Closes#16464.
[breaking-change]
floating point numbers for real.
This will break code that looks like:
let mut x = 0;
while ... {
x += 1;
}
println!("{}", x);
Change that code to:
let mut x = 0i;
while ... {
x += 1;
}
println!("{}", x);
Closes#15201.
[breaking-change]
This breaks a fair amount of code. The typical patterns are:
* `for _ in range(0, 10)`: change to `for _ in range(0u, 10)`;
* `println!("{}", 3)`: change to `println!("{}", 3i)`;
* `[1, 2, 3].len()`: change to `[1i, 2, 3].len()`.
RFC #30. Closes#6023.
[breaking-change]
Replace its usage with byte string literals, except in `bytes!()` tests.
Also add a new snapshot, to be able to use the new b"foo" syntax.
The src/etc/2014-06-rewrite-bytes-macros.py script automatically
rewrites `bytes!()` invocations into byte string literals.
Pass it filenames as arguments to generate a diff that you can inspect,
or `--apply` followed by filenames to apply the changes in place.
Diffs can be piped into `tip` or `pygmentize -l diff` for coloring.
This uncovered some dead code, most notably in middle/liveness.rs, which I think suggests there must be something fishy with that part of the code.
The #[allow(dead_code)] annotations on some of the fields I am not super happy about but as I understand, marker type may disappear at some point.
This grows a new option inside of rustdoc to add the ability to submit examples
to an external website. If the `--markdown-playground-url` command line option
or crate doc attribute `html_playground_url` is present, then examples will have
a button on hover to submit the code to the playground specified.
This commit enables submission of example code to play.rust-lang.org. The code
submitted is that which is tested by rustdoc, not necessarily the exact code
shown in the example.
Closes#14654
Now that rustdoc understands proper language tags
as the code not being Rust, we can tag everything
properly.
This change tags examples in other languages by
their language. Plain notations are marked as `text`.
Console examples are marked as `console`.
Also fix markdown.rs to not highlight non-rust code.
This is part of the ongoing renaming of the equality traits. See #12517 for more
details. All code using Eq/Ord will temporarily need to move to Partial{Eq,Ord}
or the Total{Eq,Ord} traits. The Total traits will soon be renamed to {Eq,Ord}.
cc #12517
[breaking-change]
This commit shuffles around some of the `rand` code, along with some
reorganization. The new state of the world is as follows:
* The librand crate now only depends on libcore. This interface is experimental.
* The standard library has a new module, `std::rand`. This interface will
eventually become stable.
Unfortunately, this entailed more of a breaking change than just shuffling some
names around. The following breaking changes were made to the rand library:
* Rng::gen_vec() was removed. This has been replaced with Rng::gen_iter() which
will return an infinite stream of random values. Previous behavior can be
regained with `rng.gen_iter().take(n).collect()`
* Rng::gen_ascii_str() was removed. This has been replaced with
Rng::gen_ascii_chars() which will return an infinite stream of random ascii
characters. Similarly to gen_iter(), previous behavior can be emulated with
`rng.gen_ascii_chars().take(n).collect()`
* {IsaacRng, Isaac64Rng, XorShiftRng}::new() have all been removed. These all
relied on being able to use an OSRng for seeding, but this is no longer
available in librand (where these types are defined). To retain the same
functionality, these types now implement the `Rand` trait so they can be
generated with a random seed from another random number generator. This allows
the stdlib to use an OSRng to create seeded instances of these RNGs.
* Rand implementations for `Box<T>` and `@T` were removed. These seemed to be
pretty rare in the codebase, and it allows for librand to not depend on
liballoc. Additionally, other pointer types like Rc<T> and Arc<T> were not
supported. If this is undesirable, librand can depend on liballoc and regain
these implementations.
* The WeightedChoice structure is no longer built with a `Vec<Weighted<T>>`,
but rather a `&mut [Weighted<T>]`. This means that the WeightedChoice
structure now has a lifetime associated with it.
* The `sample` method on `Rng` has been moved to a top-level function in the
`rand` module due to its dependence on `Vec`.
cc #13851
[breaking-change]
This commit moves reflection (as well as the {:?} format modifier) to a new
libdebug crate, all of which is marked experimental.
This is a breaking change because it now requires the debug crate to be
explicitly linked if the :? format qualifier is used. This means that any code
using this feature will have to add `extern crate debug;` to the top of the
crate. Any code relying on reflection will also need to do this.
Closes#12019
[breaking-change]
Rng.choose() is used so rarely that it doesn't necessitate having two
methods, especially since the failing, non-option variant also requires
Clone.
[breaking-change]
Reader.read_at_least() ensures that at least a given number of bytes
have been read. The most common use-case for this is ensuring at least 1
byte has been read. If the reader returns 0 enough times in a row, a new
error kind NoProgress will be returned instead of looping infinitely.
This change is necessary in order to properly support Readers that
repeatedly return 0, either because they're broken, or because they're
attempting to do a non-blocking read on some resource that never becomes
available.
Also add .push() and .push_at_least() methods. push() is like read() but
the results are appended to the passed Vec.
Remove Reader.fill() and Reader.push_exact() as they end up being thin
wrappers around read_at_least() and push_at_least().
[breaking-change]
