match on a tuple

Leap
Leap in Scala 
object Leap {
  def leapYear(year: Int): Boolean =
    (year % 4, year % 100, year % 400) match {
      case (_, _, 0) => true
      case (_, 0, _) => false
      case (0, _, _) => true
      case (_, _, _) => false
    }
}

A tuple is made from the conditions for the year being evenly divisible by 4, 100 and 400.

The tuple is tested in a match. It checks the values of the expressions in the tuple, and uses the underscore (_) to disregard a value. The last arm of the match returns false when none of the previous arms match.

year year % 4 year % 100 year % 400 is leap year
2020 0 20 20 true
2019 3 19 19 false
2000 0 0 0 true
1900 0 0 300 false

Although some may consider it to be a more "functional" approach, the match on a tuple approach is somewhat more verbose than other approaches, and may also be considered less readable.

16th Aug 2024 · Found it useful?

Other Approaches to Leap in Scala

Other ways our community solved this exercise
def leapYear(year: Int): Boolean =
  year % 4 == 0 && (year % 100 != 0 || year % 400 == 0)
Boolean chain

Use a chain of boolean expressions. 

def leapYear(year: Int): Boolean =
  if (year % 100 == 0) year % 400 == 0
  else year % 4 == 0
Ternary expression

Use a ternary expression of boolean conditions. 

import java.time.{LocalDate, Month}

object Leap {
  def leapYear(year: Int): Boolean =
    LocalDate.of(year, Month.FEBRUARY, 28).plusDays(1).getDayOfMonth() == 29
}
LocalDate plusDays

Use LocalDate plusDays. 

import java.time.{Year}

object Leap {
  def leapYear(year: Int): Boolean =
    Year.of(year).isLeap()
}
Built-in method

Use the built-in method.