Crate conditional_assignment

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conditional-assignment

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This is a very simple, small crate to help make conditional assignments more ergonomic.

Minimum Supported Rust Version (MSRV)

According to cargo-msrv, the MSRV is 1.56.1. Given how simple this crate is, I wouldn’t be surprised if the MSRV is lower, but I didn’t check. Try it!

Why

Sometimes this:

ⓘ
let outcome = condition.pick(positive, negative)

looks better than this:

ⓘ
let outcome = if condition {
    positive
} else {
    negative
}

Examples

Below are a few examples. See tests for more. These are just examples to show the concept. If you find yourself nesting lots of picks, there is probably a better/prettier way. Chaining picks seems better, but still within reason. In some situations map makes more sense.

// Bring the trait into scope so you can use it.
use conditional_assignment::ConditionalAssignment;

// Return a response string depending on whether
// the bool is true or false.
fn get_response_string(correct: bool) -> String {
    correct.pick(
        "That's correct, well done!",
        "Not quite, try again!"
    ).to_owned()
}

// Determine if a number is a multiple of 2, 3, and 5.
fn multiple_of_2_3_5(num: u32) -> bool {
    (num % 2 == 0).pick(
        (num % 3 == 0).pick(
            (num % 5 == 0).pick(
                true,
                false
            ),
            false
        ),
        false,
    )
}

// Get whether a &str is lowercase and get its length. 
// If the &str is none, returns (None, None).
// If the &str is empty, return (None, Some(0)).
// If the &str is not empty, return (Some(<is lowercase>), Some(<length>)).
// ...
// Except not really! `a.unwrap()` can panic, because it gets evaluated before
// we know that the `Option<&str>` is `Some(&str)`
fn is_all_lower_and_len(a: Option<&str>) -> (Option<bool>, Option<usize>) {
    a.pick(
        {
            let a = a.unwrap(); // This can panic! :(
            let len_a = a.len();

            (
                (len_a == 0).pick(None, Some(a == a.to_lowercase())),
                Some(len_a),
            )
        },
        (None, None),
    )
}

License

Licensed under either of

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Traits