LISP programmers know the value of everything, but the cost of nothing. —Alan Perlis, epigram

Error Handling

I knew if I stayed around long enough, something like this would happen. —George Bernard Shaw on dying

use std::error::Error;
use std::io::{Write,stderr};

fn print_error(mut err: &dyn Error) {
    let _ = writeln!(stderr(),"error: {}",err);
    while let Some(source) = err.source() {
        let _ = writeln!(stderr(),"cased by :{}",source);
        err = source;
    }
}

let weather = match get_weather(hometown) {
Ok(success_value) => success_value,
Err(err) => return Err(err)
};

Crates and Modules

mod spores {
use cells::{Cell, Gene};
/// A cell made by an adult fern. It disperses on the wind as part of
/// the fern life cycle. A spore grows into a prothallus -- a whole
/// separate organism, up to 5mm across -- which produces the zygote
/// that grows into a new fern. (Plant sex is complicated.)
pub struct Spore {
...
}
/// Simulate the production of a spore by meiosis.
pub fn produce_spore(factory: &mut Sporangium) -> Spore {
...
}
/// Extract the genes in a particular spore.
pub(crate) fn genes(spore: &Spore) -> Vec<Gene> {
...
}
/// Mix genes to prepare for meiosis (part of interphase).
fn recombine(parent: &mut Cell) {
...
}
...
}

bin

Attributes

Test

#[test]
fn trig_works() {
use std::f64::consts::PI;
assert!(roughly_equal(PI.sin(), 0.0));
}



```rust
#[cfg(test)] // 仅当run test时才会include 这个模块 
// include this module only when testing
mod tests {
fn roughly_equal(a: f64, b: f64) -> bool {
(a - b).abs() < 1e-6
}
#[test]
fn trig_works() {
use std::f64::consts::PI;
assert!(roughly_equal(PI.sin(), 0.0));
}
}

Documentation

Package Versions