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https://github.com/rust-lang-nursery/rust-cookbook
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Basics: update random number distributions; tweaks to other prior rand sections
This commit is contained in:
Diggory Hardy
Brian Anderson
parent
b3b5154521
commit
c399dc4b7d
2 changed files with 28 additions and 27 deletions
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@ -4,9 +4,9 @@
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|--------|--------|------------|
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| [Read lines of strings from a file][ex-std-read-lines] | [![std-badge]][std] | [![cat-filesystem-badge]][cat-filesystem] |
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| [Read and write integers in little-endian byte order][ex-byteorder-le] | [![byteorder-badge]][byteorder] | [![cat-encoding-badge]][cat-encoding] |
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| [Generate random numbers for simple types][ex-rand-simple] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
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| [Generate random numbers][ex-rand] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
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| [Generate random numbers within a range][ex-rand-range] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
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| [Generate random numbers with normal distribution][ex-rand-dist] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
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| [Generate random distributions][ex-rand-dist] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
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| [Generate random values of a custom type][ex-rand-custom] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
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| [Run an external command and process stdout][ex-parse-subprocess-output] | [![regex-badge]][regex] | [![cat-os-badge]][cat-os] [![cat-text-processing-badge]][cat-text-processing] |
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| [Filter a log file by matching multiple regular expressions][ex-regex-filter-log] | [![regex-badge]][regex] | [![cat-text-processing-badge]][cat-text-processing]
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@ -115,11 +115,11 @@ fn decode(mut bytes: &[u8]) -> Result<Payload> {
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# quick_main!(run);
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```
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[ex-rand-simple]: #ex-rand-simple
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<a name="ex-rand-simple"></a>
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## Generate random numbers for simple types
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[ex-rand]: #ex-rand
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<a name="ex-rand"></a>
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## Generate random numbers
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The `rand` crate provides a convenient source of psuedo-random numbers.
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The [`rand`] crate provides a convenient source of psuedo-random numbers.
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[![rand-badge]][rand] [![cat-science-badge]][cat-science]
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@ -132,26 +132,16 @@ fn main() {
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let mut rng = rand::thread_rng();
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// Integers are uniformly distributed over the type's whole range:
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let n1: u32 = rng.gen();
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let n1: u8 = rng.gen();
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let n2: u16 = rng.gen();
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let n3: u8 = rng.gen();
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println!("Random u32, u16, u8: {}, {}, {}", n1, n2, n3);
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println!("Random u8: {}; random u16: {}", n1, n2);
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println!("Random i32: {}", rng.gen::<i32>());
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// Floating point numbers are uniformly distributed in the half-open range [0, 1)
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println!("Random float: {}", rng.gen::<f64>());
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println!("Random floats: {:?}", (0..5).map(|_| rng.gen()).collect::<Vec<f32>>());
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}
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```
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Example output:
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```
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Random u32, u16, u8: 1224630198, 31187, 43
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Random i32: -515338046
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Random float: 0.7258180295601702
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Random floats: [0.6633928, 0.4400041, 0.49633145, 0.02997303, 0.41612816]
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```
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[ex-rand-range]: #ex-rand-range
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<a name="ex-rand-range"></a>
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## Generate random numbers within a range
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@ -172,7 +162,7 @@ fn main() {
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}
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```
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Alternatively, one can use the [`Range`](https://doc.rust-lang.org/rand/rand/distributions/range/struct.Range.html) distribution.
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Alternatively, one can use the [`Range`] distribution (otherwise known as uniform).
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This has the same effect, but may be faster when repeatedly generating numbers
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in the same range.
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@ -198,12 +188,17 @@ fn main() {
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[ex-rand-dist]: #ex-rand-dist
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<a name="ex-rand-dist"></a>
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## Generate random numbers with normal distribution
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## Random number distributions
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[![rand-badge]][rand] [![cat-science-badge]][cat-science]
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Creates a [`Normal`] distribution with mean `3` and standard deviation `5`
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and generates a random value with [`IndependentSample::ind_sample`].
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You've already seen how to create numbers with uniform distribution [above][ex-rand-range]
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(using [`Range`]). Other distributions are used in the same way: create a distribution, then
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sample from that distribution (using [`IndependentSample::ind_sample`]) with the help of
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a random-number generator (`rng`).
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The [distributions available are documented here][rand-distributions]. An example using the
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[`Normal`] distribution is shown below.
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```rust
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extern crate rand;
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@ -211,10 +206,12 @@ extern crate rand;
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use rand::distributions::{Normal, IndependentSample};
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fn main() {
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let normal = Normal::new(3.0, 5.0);
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let mut rng = rand::thread_rng();
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// mean 2, standard deviation 3:
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let normal = Normal::new(2.0, 3.0);
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let v = normal.ind_sample(&mut rng);
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println!("{} is from a N(3, 25) distribution", v)
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println!("{} is from a N(2, 9) distribution", v)
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}
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```
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@ -800,9 +797,13 @@ fn run() -> Result<()> {
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[`Read`]: https://doc.rust-lang.org/std/io/trait.Read.html
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[`Normal`]: https://doc.rust-lang.org/rand/rand/distributions/normal/struct.Normal.html
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[`IndependentSample::ind_sample`]: https://doc.rust-lang.org/rand/rand/distributions/trait.IndependentSample.html#tymethod.ind_sample
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[`rand`]: https://doc.rust-lang.org/rand
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[`Rng::gen_range`]: https://doc.rust-lang.org/rand/rand/trait.Rng.html#method.gen_range
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[`Regex::captures_iter`]: https://doc.rust-lang.org/regex/regex/struct.Regex.html#method.captures_iter
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[`Regex::replace_all`]: https://docs.rs/regex/0.2.2/regex/struct.Regex.html#method.replace_all
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[`rand::Rand`]: https://doc.rust-lang.org/rand/rand/trait.Rand.html
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[`Range`]: https://doc.rust-lang.org/rand/rand/distributions/range/struct.Range.html
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[rand-distributions]: https://doc.rust-lang.org/rand/rand/distributions/index.html
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[`Regex`]: https://doc.rust-lang.org/regex/regex/struct.Regex.html
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[`rand::Rand`]: https://doc.rust-lang.org/rand/rand/trait.Rand.html
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[`regex::RegexSetBuilder`]: https://doc.rust-lang.org/regex/regex/struct.RegexSetBuilder.html
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@ -22,9 +22,9 @@ community. It needs and welcomes help. For details see
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|--------|--------|------------|
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| [Read lines of strings from a file][ex-std-read-lines] | [![std-badge]][std] | [![cat-filesystem-badge]][cat-filesystem] |
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| [Read and write integers in little-endian byte order][ex-byteorder-le] | [![byteorder-badge]][byteorder] | [![cat-encoding-badge]][cat-encoding] |
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| [Generate random floating point numbers][ex-rand-float] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
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| [Generate random numbers][ex-rand] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
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| [Generate random numbers within a range][ex-rand-range] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
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| [Generate random numbers with normal distribution][ex-rand-dist] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
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| [Generate random number distributions][ex-rand-dist] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
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| [Generate random values of a custom type][ex-rand-custom] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
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| [Run an external command and process stdout][ex-parse-subprocess-output] | [![regex-badge]][regex] | [![cat-os-badge]][cat-os] [![cat-text-processing-badge]][cat-text-processing] |
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| [Filter a log file by matching multiple regular expressions][ex-regex-filter-log] | [![regex-badge]][regex] | [![cat-text-processing-badge]][cat-text-processing]
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@ -264,7 +264,7 @@ Keep lines sorted.
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[ex-phone]: basics.html#ex-phone
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[ex-rand-custom]: basics.html#ex-rand-custom
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[ex-rand-dist]: basics.html#ex-rand-dist
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[ex-rand-float]: basics.html#ex-rand-float
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[ex-rand]: basics.html#ex-rand
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[ex-rand-range]: basics.html#ex-rand-range
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[ex-random-port-tcp]: net.html#ex-random-port-tcp
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[ex-rayon-iter-mut]: concurrency.html#ex-rayon-iter-mut
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