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Basics: update random number distributions; tweaks to other prior rand sections

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Diggory Hardy 2017-07-24 12:39:50 +01:00 committed by Brian Anderson
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49
src/basics.md
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@ -4,9 +4,9 @@
|--------|--------|------------| |--------|--------|------------|
| [Read lines of strings from a file][ex-std-read-lines] | [![std-badge]][std] | [![cat-filesystem-badge]][cat-filesystem] | | [Read lines of strings from a file][ex-std-read-lines] | [![std-badge]][std] | [![cat-filesystem-badge]][cat-filesystem] |
| [Read and write integers in little-endian byte order][ex-byteorder-le] | [![byteorder-badge]][byteorder] | [![cat-encoding-badge]][cat-encoding] | | [Read and write integers in little-endian byte order][ex-byteorder-le] | [![byteorder-badge]][byteorder] | [![cat-encoding-badge]][cat-encoding] |
| [Generate random numbers for simple types][ex-rand-simple] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] | | [Generate random numbers][ex-rand] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
| [Generate random numbers within a range][ex-rand-range] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] | | [Generate random numbers within a range][ex-rand-range] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
| [Generate random numbers with normal distribution][ex-rand-dist] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] | | [Generate random distributions][ex-rand-dist] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
| [Generate random values of a custom type][ex-rand-custom] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] | | [Generate random values of a custom type][ex-rand-custom] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
| [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] | | [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] |
| [Filter a log file by matching multiple regular expressions][ex-regex-filter-log] | [![regex-badge]][regex] | [![cat-text-processing-badge]][cat-text-processing] | [Filter a log file by matching multiple regular expressions][ex-regex-filter-log] | [![regex-badge]][regex] | [![cat-text-processing-badge]][cat-text-processing]
@ -115,11 +115,11 @@ fn decode(mut bytes: &[u8]) -> Result<Payload> {
# quick_main!(run); # quick_main!(run);
``` ```
[ex-rand-simple]: #ex-rand-simple [ex-rand]: #ex-rand
<a name="ex-rand-simple"></a> <a name="ex-rand"></a>
## Generate random numbers for simple types ## Generate random numbers
The `rand` crate provides a convenient source of psuedo-random numbers. The [`rand`] crate provides a convenient source of psuedo-random numbers.
[![rand-badge]][rand] [![cat-science-badge]][cat-science] [![rand-badge]][rand] [![cat-science-badge]][cat-science]
@ -132,26 +132,16 @@ fn main() {
let mut rng = rand::thread_rng(); let mut rng = rand::thread_rng();
// Integers are uniformly distributed over the type's whole range: // Integers are uniformly distributed over the type's whole range:
let n1: u32 = rng.gen(); let n1: u8 = rng.gen();
let n2: u16 = rng.gen(); let n2: u16 = rng.gen();
let n3: u8 = rng.gen(); println!("Random u8: {}; random u16: {}", n1, n2);
println!("Random u32, u16, u8: {}, {}, {}", n1, n2, n3);
println!("Random i32: {}", rng.gen::<i32>()); println!("Random i32: {}", rng.gen::<i32>());
// Floating point numbers are uniformly distributed in the half-open range [0, 1) // Floating point numbers are uniformly distributed in the half-open range [0, 1)
println!("Random float: {}", rng.gen::<f64>()); println!("Random float: {}", rng.gen::<f64>());
println!("Random floats: {:?}", (0..5).map(|_| rng.gen()).collect::<Vec<f32>>());
} }
``` ```
Example output:
```
Random u32, u16, u8: 1224630198, 31187, 43
Random i32: -515338046
Random float: 0.7258180295601702
Random floats: [0.6633928, 0.4400041, 0.49633145, 0.02997303, 0.41612816]
```
[ex-rand-range]: #ex-rand-range [ex-rand-range]: #ex-rand-range
<a name="ex-rand-range"></a> <a name="ex-rand-range"></a>
## Generate random numbers within a range ## Generate random numbers within a range
@ -172,7 +162,7 @@ fn main() {
} }
``` ```
Alternatively, one can use the [`Range`](https://doc.rust-lang.org/rand/rand/distributions/range/struct.Range.html) distribution. Alternatively, one can use the [`Range`] distribution (otherwise known as uniform).
This has the same effect, but may be faster when repeatedly generating numbers This has the same effect, but may be faster when repeatedly generating numbers
in the same range. in the same range.
@ -198,12 +188,17 @@ fn main() {
[ex-rand-dist]: #ex-rand-dist [ex-rand-dist]: #ex-rand-dist
<a name="ex-rand-dist"></a> <a name="ex-rand-dist"></a>
## Generate random numbers with normal distribution ## Random number distributions
[![rand-badge]][rand] [![cat-science-badge]][cat-science] [![rand-badge]][rand] [![cat-science-badge]][cat-science]
Creates a [`Normal`] distribution with mean `3` and standard deviation `5` You've already seen how to create numbers with uniform distribution [above][ex-rand-range]
and generates a random value with [`IndependentSample::ind_sample`]. (using [`Range`]). Other distributions are used in the same way: create a distribution, then
sample from that distribution (using [`IndependentSample::ind_sample`]) with the help of
a random-number generator (`rng`).
The [distributions available are documented here][rand-distributions]. An example using the
[`Normal`] distribution is shown below.
```rust ```rust
extern crate rand; extern crate rand;
@ -211,10 +206,12 @@ extern crate rand;
use rand::distributions::{Normal, IndependentSample}; use rand::distributions::{Normal, IndependentSample};
fn main() { fn main() {
let normal = Normal::new(3.0, 5.0);
let mut rng = rand::thread_rng(); let mut rng = rand::thread_rng();
// mean 2, standard deviation 3:
let normal = Normal::new(2.0, 3.0);
let v = normal.ind_sample(&mut rng); let v = normal.ind_sample(&mut rng);
println!("{} is from a N(3, 25) distribution", v) println!("{} is from a N(2, 9) distribution", v)
} }
``` ```
@ -800,9 +797,13 @@ fn run() -> Result<()> {
[`Read`]: https://doc.rust-lang.org/std/io/trait.Read.html [`Read`]: https://doc.rust-lang.org/std/io/trait.Read.html
[`Normal`]: https://doc.rust-lang.org/rand/rand/distributions/normal/struct.Normal.html [`Normal`]: https://doc.rust-lang.org/rand/rand/distributions/normal/struct.Normal.html
[`IndependentSample::ind_sample`]: https://doc.rust-lang.org/rand/rand/distributions/trait.IndependentSample.html#tymethod.ind_sample [`IndependentSample::ind_sample`]: https://doc.rust-lang.org/rand/rand/distributions/trait.IndependentSample.html#tymethod.ind_sample
[`rand`]: https://doc.rust-lang.org/rand
[`Rng::gen_range`]: https://doc.rust-lang.org/rand/rand/trait.Rng.html#method.gen_range [`Rng::gen_range`]: https://doc.rust-lang.org/rand/rand/trait.Rng.html#method.gen_range
[`Regex::captures_iter`]: https://doc.rust-lang.org/regex/regex/struct.Regex.html#method.captures_iter [`Regex::captures_iter`]: https://doc.rust-lang.org/regex/regex/struct.Regex.html#method.captures_iter
[`Regex::replace_all`]: https://docs.rs/regex/0.2.2/regex/struct.Regex.html#method.replace_all [`Regex::replace_all`]: https://docs.rs/regex/0.2.2/regex/struct.Regex.html#method.replace_all
[`rand::Rand`]: https://doc.rust-lang.org/rand/rand/trait.Rand.html
[`Range`]: https://doc.rust-lang.org/rand/rand/distributions/range/struct.Range.html
[rand-distributions]: https://doc.rust-lang.org/rand/rand/distributions/index.html
[`Regex`]: https://doc.rust-lang.org/regex/regex/struct.Regex.html [`Regex`]: https://doc.rust-lang.org/regex/regex/struct.Regex.html
[`rand::Rand`]: https://doc.rust-lang.org/rand/rand/trait.Rand.html [`rand::Rand`]: https://doc.rust-lang.org/rand/rand/trait.Rand.html
[`regex::RegexSetBuilder`]: https://doc.rust-lang.org/regex/regex/struct.RegexSetBuilder.html [`regex::RegexSetBuilder`]: https://doc.rust-lang.org/regex/regex/struct.RegexSetBuilder.html

6
src/intro.md
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@ -22,9 +22,9 @@ community. It needs and welcomes help. For details see
|--------|--------|------------| |--------|--------|------------|
| [Read lines of strings from a file][ex-std-read-lines] | [![std-badge]][std] | [![cat-filesystem-badge]][cat-filesystem] | | [Read lines of strings from a file][ex-std-read-lines] | [![std-badge]][std] | [![cat-filesystem-badge]][cat-filesystem] |
| [Read and write integers in little-endian byte order][ex-byteorder-le] | [![byteorder-badge]][byteorder] | [![cat-encoding-badge]][cat-encoding] | | [Read and write integers in little-endian byte order][ex-byteorder-le] | [![byteorder-badge]][byteorder] | [![cat-encoding-badge]][cat-encoding] |
| [Generate random floating point numbers][ex-rand-float] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] | | [Generate random numbers][ex-rand] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
| [Generate random numbers within a range][ex-rand-range] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] | | [Generate random numbers within a range][ex-rand-range] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
| [Generate random numbers with normal distribution][ex-rand-dist] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] | | [Generate random number distributions][ex-rand-dist] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
| [Generate random values of a custom type][ex-rand-custom] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] | | [Generate random values of a custom type][ex-rand-custom] | [![rand-badge]][rand] | [![cat-science-badge]][cat-science] |
| [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] | | [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] |
| [Filter a log file by matching multiple regular expressions][ex-regex-filter-log] | [![regex-badge]][regex] | [![cat-text-processing-badge]][cat-text-processing] | [Filter a log file by matching multiple regular expressions][ex-regex-filter-log] | [![regex-badge]][regex] | [![cat-text-processing-badge]][cat-text-processing]
@ -264,7 +264,7 @@ Keep lines sorted.
[ex-phone]: basics.html#ex-phone [ex-phone]: basics.html#ex-phone
[ex-rand-custom]: basics.html#ex-rand-custom [ex-rand-custom]: basics.html#ex-rand-custom
[ex-rand-dist]: basics.html#ex-rand-dist [ex-rand-dist]: basics.html#ex-rand-dist
[ex-rand-float]: basics.html#ex-rand-float [ex-rand]: basics.html#ex-rand
[ex-rand-range]: basics.html#ex-rand-range [ex-rand-range]: basics.html#ex-rand-range
[ex-random-port-tcp]: net.html#ex-random-port-tcp [ex-random-port-tcp]: net.html#ex-random-port-tcp
[ex-rayon-iter-mut]: concurrency.html#ex-rayon-iter-mut [ex-rayon-iter-mut]: concurrency.html#ex-rayon-iter-mut