fn main() { 
    println!("value is {}", *helper());
}

fn helper() -> &u64 {
    let a = 42;
    &a
}

error[E0106]: missing lifetime specifier
 --> src/main.rs:5:16
  |
5 | fn helper() -> &u64 {
  |                ^ expected named lifetime parameter
  |
  = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from
help: consider using the `'static` lifetime
  |
5 | fn helper() -> &'static u64 {
  |                 +++++++

For more information about this error, try `rustc --explain E0106`.
error: could not compile `playground` (bin "playground") due to previous error

fn main() { 
    println!("value is {}", *helper());
}

fn helper() -> &'static u64 {
    let a = 42;
    &a
}

error[E0515]: cannot return reference to local variable `a`
 --> src/main.rs:7:5
  |
7 |     &a
  |     ^^ returns a reference to data owned by the current function

For more information about this error, try `rustc --explain E0515`.

#![no_main]
#![no_std]

use embedded_hal::digital::v2::InputPin;
use embedded_hal::digital::v2::OutputPin;
use nrf52832_hal as hal;
use nrf52832_hal::gpio::Level;
use rtt_target::{rprintln, rtt_init_print};

#[panic_handler] // panicking behavior
fn panic(_: &core::panic::PanicInfo) -> ! {
    loop {
        cortex_m::asm::bkpt();
    }
}

#[cortex_m_rt::entry]
fn main() -> ! {

    rtt_init_print!();
    let p = hal::pac::Peripherals::take().unwrap();
    let port0 = hal::gpio::p0::Parts::new(p.P0);
    let button = port0.p0_13.into_pullup_input();
    let mut led = port0.p0_17.into_push_pull_output(Level::Low);

    rprintln!("Blinky button demo starting");
    loop {
        if button.is_high().unwrap() {
            led.set_high().unwrap();
        } else {
            led.set_low().unwrap();
        }
    }
}

#![no_main]
#![no_std]

use embedded_hal::digital::v2::InputPin;
use embedded_hal::digital::v2::OutputPin;
use nrf52832_hal as hal;
use nrf52832_hal::gpio::Level;
use rtt_target::{rprintln, rtt_init_print};

#[panic_handler] // panicking behavior
fn panic(_: &core::panic::PanicInfo) -> ! {
    loop {
        cortex_m::asm::bkpt();
    }
}

#[cortex_m_rt::entry]
fn main() -> ! {
    rtt_init_print!();
    let p = hal::pac::Peripherals::take().unwrap();
    let port0 = hal::gpio::p0::Parts::new(p.P0);
    let button = port0.p0_13.into_pullup_input();
    let mut led = port0.p0_17.into_push_pull_output(Level::Low);

    rprintln!("Blinky button demo starting");
    loop {
        if button.is_high().unwrap() {
            led.set_high().unwrap();
        } else {
            led.set_low().unwrap();
        }
    }
}