or-else-map

Fix Option::map_or_else and Result::map_or_else, to make sense.

Why?

• Option::map_or_else and Result::map_or_else were presumably written by yoda; the map and or_else are reversed from what they should be.
• "if you aint first you're last" (Bobby, et al., 2006)

Example

use or_else_map::prelude::*;

fn option_eg() {
    let x = Some(2);
    let y = x.map_or_else(|| 0, |v| v * 2); // yoda
    let z = x.or_else_map(|| 0, |v| v * 2); // not-yoda
    assert_eq!(y, 4);
    assert_eq!(z, 4);

    let x: Option<i32> = None;
    let z = x.or_else_map(|| 0, |v| v * 2);
    assert_eq!(z, 0);
}

fn result_eg() {
    let x: Result<i32, &str> = Ok(2);
    let y = x.map_or_else(|e| 0, |v| v * 2); // yoda
    let z = x.or_else_map(|e| 0, |v| v * 2); // not-yoda
    assert_eq!(y, 4);
    assert_eq!(z, 4);

    let x: Result<i32, &str> = Err("oof");
    let z = x.or_else_map(|e| 0, |v| v * 2);
    assert_eq!(z, 0);
}

fn main() {
    option_eg();
    result_eg();
}

Acknowledgements

• my fans and family
• the academy and the hollywood foreign press
• the rust developers