在#[no_std]下执行数学运算

    2. #![no_std]
    4. use panic_halt as _;
    6. use cortex_m_rt::entry;
    7. use cortex_m_semihosting::{debug, hprintln};
    8. use libm::{exp, floorf, sin, sqrtf};
    10. #[entry]
    11. fn main() -> ! {
    12.     let floored_float = floorf(float);
    14.     let sqrt_of_four = sqrtf(floored_float);
    16.     let sinus_of_four = sin(floored_float.into());
    18.     let exponential_of_four = exp(floored_float.into());
    19.     hprintln!("Floored test float {} to {}", float, floored_float).unwrap();
    20.     hprintln!("The square root of {} is {}", floored_float, sqrt_of_four).unwrap();
    21.     hprintln!("The sinus of four is {}", sinus_of_four).unwrap();
    23.         exponential_of_four
    24.     )
    25.     .unwrap();
    26.     // 退出QEMU
    27.     // 注意不要在硬件上允许这个; 它能破坏OpenOCD的状态
    28.     // debug::exit(debug::EXIT_SUCCESS);
    30.     loop {}
    31. }