This commit carries out the request from issue #14678:
> The method `Iterator::len()` is surprising, as all the other uses of
> `len()` do not consume the value. `len()` would make more sense to be
> called `count()`, but that would collide with the current
> `Iterator::count(|T| -> bool) -> unit` method. That method, however, is
> a bit redundant, and can be easily replaced with
> `iter.filter(|x| x < 5).count()`.
> After this change, we could then define the `len()` method
> on `iter::ExactSize`.
Closes#14678.
[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 functionality is not super-core and so doesn't need to be included
in std. It's possible that std may need rand (it does a little bit now,
for io::test) in which case the functionality required could be moved to
a secret hidden module and reexposed by librand.
Unfortunately, using #[deprecated] here is hard: there's too much to
mock to make it feasible, since we have to ensure that programs still
typecheck to reach the linting phase.
The `print!` and `println!` macros are now the preferred method of printing, and so there is no reason to export the `stdio` functions in the prelude. The functions have also been replaced by their macro counterparts in the tutorial and other documentation so that newcomers don't get confused about what they should be using.
This commit uniforms the short title of modules provided by libstd,
in order to make their roles more explicit when glancing at the index.
Signed-off-by: Luca Bruno <lucab@debian.org>
Provide `Closed01` and `Open01` that generate directly from the
closed/open intervals from 0 to 1, in contrast to the plain impls for
f32 and f64 which generate the half-open [0,1).
Fixes#7755.
- Adds the `Sample` and `IndependentSample` traits for generating numbers where there are parameters (e.g. a list of elements to draw from, or the mean/variance of a normal distribution). The former takes `&mut self` and the latter takes `&self` (this is the only difference).
- Adds proper `Normal` and `Exp`-onential distributions
- Adds `Range` which generates `[lo, hi)` generically & properly (via a new trait) replacing the incorrect behaviour of `Rng.gen_integer_range` (this has become `Rng.gen_range` for convenience, it's far more efficient to use `Range` itself)
- Move the `Weighted` struct from `std::rand` to `std::rand::distributions` & improve it
- optimisations and docs
This reifies the computations required for uniformity done by
(the old) `Rng.gen_integer_range` (now Rng.gen_range), so that they can
be amortised over many invocations, if it is called in a loop.
Also, it makes it correct, but using a trait + impls for each type,
rather than trying to coerce `Int` + `u64` to do the right thing. This
also makes it more extensible, e.g. big integers could & should
implement SampleRange.
It now:
- can be explicitly seeded from user code (`seed_task_rng`) or from the
environment (`RUST_SEED`, a positive integer)
- automatically reseeds itself from the OS *unless* it was seeded by
either method above
- has more documentation
This provides 2 methods: .reseed() and ::from_seed that modify and
create respecitively.
Implement this trait for the RNGs in the stdlib for which this makes
sense.
This is implemented as a wrapper around another RNG. It is designed
to allow the actual implementation to be changed without changing
the external API (e.g. it currently uses a 64-bit generator on 64-
bit platforms, and a 32-bit one on 32-bit platforms; but one could
imagine that the IsaacRng may be deprecated later, and having this
ability to switch algorithms without having to update the points of
use is convenient.)
This is the recommended general use RNG.
The former reads from e.g. /dev/urandom, the latter just wraps any
std::rt::io::Reader into an interface that implements Rng.
This also adds Rng.fill_bytes for efficient implementations of the above
(reading 8 bytes at a time is inefficient when you can read 1000), and
removes the dependence on src/rt (i.e. rand_gen_seed) although this last
one requires implementing hand-seeding of the XorShiftRng used in the
scheduler on Linux/unixes, since OSRng relies on a scheduler existing to
be able to read from /dev/urandom.
This is 2x faster on 64-bit computers at generating anything larger
than 32-bits.
It has been verified against the canonical C implementation from the
website of the creator of ISAAC64.
Also, move `Rng.next` to `Rng.next_u32` and add `Rng.next_u64` to
take full advantage of the wider word width; otherwise Isaac64 will
always be squeezed down into a u32 wasting half the entropy and
offering no advantage over the 32-bit variant.
This PR solves one of the pain points with c-style enums. Simplifies writing a fn to convert from an int/uint to an enum. It does this through a `#[deriving(FromPrimitive)]` syntax extension.
Before this is committed though, we need to discuss if `ToPrimitive`/`FromPrimitive` has the right design (cc #4819). I've changed all the `.to_int()` and `from_int()` style functions to return `Option<int>` so we can handle partial functions. For this PR though only enums and `extra::num::bigint::*` take advantage of returning None for unrepresentable values. In the long run it'd be better if `i64.to_i8()` returned `None` if the value was too large, but I'll save this for a future PR.
Closes#3868.
