Boolean one line

Leap
Leap in Rust 
pub fn is_leap_year(year: u64) -> bool {
    (year % 4 == 0) && ((year % 100 != 0) || (year % 400 == 0))
}

The first boolean condition uses the remainder operator to check if the year is evenly divided by 4.

  • If the year is not evenly divisible by 4, then the chain will "short circuit" due to the next operator being a logical AND (&&), and will return false.
  • If the year is evenly divisible by 4, then the year is checked to not be evenly divisible by 100.
  • If the year is not evenly divisible by 100, then the expression is true and the chain will "short-circuit" to return true, since the next operator is a logical OR (||).
  • If the year is evenly divisible by 100, then the expression is false, and the returned value from the chain will be if the year is evenly divisible by 400.
year year % 4 == 0 year % 100 != 0 year % 400 == 0 is leap year
2020 true true not evaluated true
2019 false not evaluated not evaluated false
2000 true false true true
1900 true false false false

The chain of boolean expressions is efficient, as it proceeds from testing the most likely to least likely conditions.

6th Nov 2024 · Found it useful?

Other Approaches to Leap in Rust

Other ways our community solved this exercise
pub fn is_leap_year(year: u64) -> bool {
    if year % 100 == 0 {
        year % 400 == 0
    } else {
        year % 4 == 0
    }
}
Ternary operator

Use a ternary expression of boolean conditions. 

pub fn is_leap_year(year: u64) -> bool {
    match (year % 4, year % 100, year % 400) {
        (_, _, 0) => true,
        (_, 0, _) => false,
        (0, _, _) => true,
        _ => false,
    }
}
match on a tuple

Use a match on a tuple made from boolean conditions. 

use time::{Date, Duration, Month};

pub fn is_leap_year(year: u64) -> bool {
    (Date::from_calendar_date(year as i32, Month::February, 28).unwrap() + Duration::DAY).day()
        == 29
}
Date addition with time crate

Use time::Date addition. 

use chrono::{prelude::*, Duration};

pub fn is_leap_year(year: u64) -> bool {
    (Utc.ymd(year as i32, 2, 28) + Duration::days(1)).day() == 29
}
Date addition with chrono crate

Use chrono::Date addition.