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| <h1 id="performing-math-functionality-with-no_std"><a class="header" href="#performing-math-functionality-with-no_std">Performing math functionality with <code>#[no_std]</code></a></h1> |
| <p>If you want to perform math related functionality like calculating the squareroot or |
| the exponential of a number and you have the full standard library available, your code |
| might look like this:</p> |
| <pre><code class="language-rs">//! 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 |
| ) |
| } |
| </code></pre> |
| <p>Without standard library support, these functions are not available. |
| An external crate like <a href="https://crates.io/crates/libm"><code>libm</code></a> can be used instead. The example code |
| would then look like this:</p> |
| <pre><code class="language-rs">#![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 {} |
| } |
| </code></pre> |
| <p>If you need to perform more complex operations like DSP signal processing or advanced linear |
| algebra on your MCU, the following crates might help you</p> |
| <ul> |
| <li><a href="https://github.com/jacobrosenthal/cmsis-dsp-sys">CMSIS DSP library binding</a></li> |
| <li><a href="https://crates.io/crates/constgebra"><code>constgebra</code></a></li> |
| <li><a href="https://github.com/tarcieri/micromath"><code>micromath</code></a></li> |
| <li><a href="https://crates.io/crates/microfft"><code>microfft</code></a></li> |
| <li><a href="https://github.com/dimforge/nalgebra"><code>nalgebra</code></a></li> |
| </ul> |
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