Suppose a situation when you need to check the integer variable c is greater than or equal to a and less than or equal to b. To do that you may write something like below:
val within = a <= c && c <= bThis code works well. But Kotlin provides a more convenient way to do the same using ranges:
val within = c in a..bHere, a..b is a range of numbers from a to b (inclusive both borders), in is a special keyword that is used to check whether a value is within a range. Later you will see that this keyword can be used with other types, as well.
The value of within is true if c belongs to the range inclusively, otherwise, it is false.
Here are some examples:
println(5 in 5..15) // true
println(12 in 5..15) // true
println(15 in 5..15) // true
println(20 in 5..15) // falseIf you need to exclude the right border, you may subtract one from it:
val withinExclRight = c in a..b - 1 // a <= c && c < bIf you need to check that a value is not within a range, just add
! (not) before in.val notWithin = 100 !in 10..99 // trueYou may combine ranges using standard logical operators. The code below checks that
c is within one of three ranges.val within = c in 5..10 || c in 20..30 || c in 40..50 // true if c is within at least one rangeYou can assign a range to a variable and use it later.
val range = 100..200
println(300 in range) // falseprintln('b' in 'a'..'c') // true
println('k' in 'a'..'e') // false
println("hello" in "he".."hi") // true
println("abc" in "aab".."aac") // falseNow it is enough to understand only ranges for integer numbers and characters, ranges of other types won't be considered here.