Rustでも標準で誰もが使うものが用意されている。ライブラリに相当するものをクレート(crate)と呼ぶことがある
基本的なstdにはプリミティブなデータ型やモジュール、マクロなどが定義されている
crates.ioにたくさんのパッケージがある
let f:f64 = 3.45;
let val = f.sqrt();
use std::f64;
fn main() {
let f:f64 = 3.45;
println!("{}の平方根={:?}", f, f.sqrt());
}
fn main() {
let s = "hello, dogs";
println!("{:?}", s.to_uppercase());
}
乱数はRngというトレイトを使うことができる
use rand::Rng;
fn main() {
let mut r = rand::thread_rng();
for _i in 1..6 {
println!("{}", r.gen_range(1, 11));
}
}
### クレートを使うプロジェクト
クレートの最新バージョンを調べる
$ cargo search rand
Updating crates.io index
rand = “0.8.5” # Random number generators and other randomness functionality.
tinyrand = “0.5.0” # Lightweight RNG specification and several ultrafast implementations in Rust.
bevy_rand = “0.1.0” # A plugin to integrate rand for ECS optimised RNG for the Bevy game engine.
random_derive = “0.0.0” # Procedurally defined macro for automatically deriving rand::Rand for structs and enums
faker_rand = “0.1.1” # Fake data generators for lorem ipsum, names, emails, and more
rand_derive2 = “0.1.21” # Generate customizable random types with the rand crate
fake-rand-test = “0.0.0” # Random number generators and other randomness functionality.
ndarray-rand = “0.14.0” # Constructors for randomized arrays. `rand` integration for `ndarray`.
rand_derive = “0.5.0” # `#[derive(Rand)]` macro (deprecated).
rand_core = “0.6.4” # Core random number generator traits and tools for implementation.
… and 1126 crates more (use –limit N to see more)
$ cargo new random3 –bin
Created binary (application) `random3` package
実数の数値計算
abs(), acos(), asin(), atan(), ceil(), copisign(), cos(), exp(), exp2(), floor(), fract(), ln(), log(), log10(), log2(), mul_add(), powf(), powi(), round(), signum(), sin(), sqrt(), tan(), trunc()
use std::f64;
fn main() {
let f:f64 = 3.45;
println!("{:?}", f.fract());
}
文字列の操作
find(), matches(), parse(), repeat(), to_lowercase(), to_uppercase(), trim(), trim_end(), trim_start()
乱数の生成
gen(), gen_range(), gen_bool(), gen_ratio(2, 3)
use rand::{thread_rng, Rng};
fn main() {
let mut rng = thread_rng();
for _ in 0..11 {
let x: u16 = rng.gen();
print!("{} ", x);
}
}
use rand::{thread_rng, Rng};
fn main() {
let mut rng = thread_rng();
for _ in 0..11 {
let x: u16 = rng.gen_range(0, 3);
print!("{} ", x);
}
}
### 日付日時
Date, DateTime, Duration
use chrono::{Utc, Local, DateTime};
use chrono::{Datelike, Timelike};
fn main() {
let utc: DateTime<Utc> = Utc::now();
println!("{}", utc);
let local: DateTime<Local> = Local::now();
println!("{}", local);
println!("{}/{}/{}", local.year(), local.month(), local.day());
println!("{:02}:{:02}:{:02}",
local.hour(), local.minute(), local.second());
}
use std::thread;
use std::time::Duration;
fn main() {
println!("3秒待ちます。");
thread::sleep(Duration::from_secs(3));
println!("3秒待ちました");
}
