rust/example/std_example.rs

#![feature(core_intrinsics)]

use std::io::Write;
use std::intrinsics;

fn main() {
    let _ = ::std::iter::repeat('a' as u8).take(10).collect::<Vec<_>>();
    let stderr = ::std::io::stderr();
    let mut stderr = stderr.lock();

    writeln!(stderr, "some {} text", "<unknown>").unwrap();

    let _ = std::process::Command::new("true").env("c", "d").spawn();

    println!("cargo:rustc-link-lib=z");

    static ONCE: std::sync::Once = std::sync::ONCE_INIT;
    ONCE.call_once(|| {});

    LoopState::Continue(()) == LoopState::Break(());

    // Make sure ByValPair values with differently sized components are correctly passed
    map(None::<(u8, Box<Instruction>)>);

    println!("{}", 2.3f32.exp());
    println!("{}", 2.3f32.exp2());
    println!("{}", 2.3f32.abs());
    println!("{}", 2.3f32.sqrt());
    println!("{}", 2.3f32.floor());
    println!("{}", 2.3f32.ceil());
    println!("{}", 2.3f32.min(1.0));
    println!("{}", 2.3f32.max(1.0));

    assert_eq!(0b0000000000000000000000000010000010000000000000000000000000000000_0000000000100000000000000000000000001000000000000100000000000000u128.leading_zeros(), 26);
    assert_eq!(0b0000000000000000000000000010000000000000000000000000000000000000_0000000000000000000000000000000000001000000000000000000010000000u128.trailing_zeros(), 7);

    checked_div_i128(0i128, 2i128);
    checked_div_u128(0u128, 2u128);
    assert_eq!(1u128 + 2, 3);

    assert_eq!(0b100010000000000000000000000000000u128 >> 10, 0b10001000000000000000000u128);
    assert_eq!(0xFEDCBA987654321123456789ABCDEFu128 >> 64, 0xFEDCBA98765432u128);
    assert_eq!(0xFEDCBA987654321123456789ABCDEFu128 as i128 >> 64, 0xFEDCBA98765432i128);
    assert_eq!(353985398u128 * 932490u128, 330087843781020u128);
}

#[derive(PartialEq)]
enum LoopState {
    Continue(()),
    Break(())
}

pub enum Instruction {
    Increment,
    Loop,
}

fn map(a: Option<(u8, Box<Instruction>)>) -> Option<Box<Instruction>> {
    match a {
        None => None,
        Some((_, instr)) => Some(instr),
    }
}

fn checked_div_i128(lhs: i128, rhs: i128) -> Option<i128> {
    if rhs == 0 || (lhs == -170141183460469231731687303715884105728 && rhs == -1) {
        None
    } else {
        Some(unsafe { intrinsics::unchecked_div(lhs, rhs) })
    }
}

fn checked_div_u128(lhs: u128, rhs: u128) -> Option<u128> {
    match rhs {
        0 => None,
        rhs => Some(unsafe { intrinsics::unchecked_div(lhs, rhs) })
    }
}