使用 #[no_std] 执行数学功能

如果您想执行与数学相关的功能，例如计算数字的平方根或指数，并且您拥有完整的标准库，则您的代码可能如下所示

//! Some mathematical functions with standard support available

fn main() {
    let float: f32 = 4.82832;
    let floored_float = float.floor();

    let sqrt_of_four = floored_float.sqrt();

    let sinus_of_four = floored_float.sin();

    let exponential_of_four = floored_float.exp();
    println!("Floored test float {} to {}", float, floored_float);
    println!("The square root of {} is {}", floored_float, sqrt_of_four);
    println!("The sinus of four is {}", sinus_of_four);
    println!(
        "The exponential of four to the base e is {}",
        exponential_of_four
    )
}

没有标准库支持，这些函数不可用。可以使用像 libm 这样的外部板条箱代替。示例代码如下所示

#![no_main]
#![no_std]

use panic_halt as _;

use cortex_m_rt::entry;
use cortex_m_semihosting::{debug, hprintln};
use libm::{exp, floorf, sin, sqrtf};

#[entry]
fn main() -> ! {
    let float = 4.82832;
    let floored_float = floorf(float);

    let sqrt_of_four = sqrtf(floored_float);

    let sinus_of_four = sin(floored_float.into());

    let exponential_of_four = exp(floored_float.into());
    hprintln!("Floored test float {} to {}", float, floored_float).unwrap();
    hprintln!("The square root of {} is {}", floored_float, sqrt_of_four).unwrap();
    hprintln!("The sinus of four is {}", sinus_of_four).unwrap();
    hprintln!(
        "The exponential of four to the base e is {}",
        exponential_of_four
    )
    .unwrap();
    // exit QEMU
    // NOTE do not run this on hardware; it can corrupt OpenOCD state
    // debug::exit(debug::EXIT_SUCCESS);

    loop {}
}

如果您需要在 MCU 上执行更复杂的操作，例如 DSP 信号处理或高级线性代数，以下板条箱可能对您有所帮助

• CMSIS DSP 库绑定
• constgebra
• micromath
• microfft
• nalgebra