Exploring the plus and minus operators for immutable lists in Kotlin

example.kt

// TLDR: If you use list - [element] then it will remove the first occurrance of that element.
//  If you use list - listOf([element]) then it will remove all occrrances of that element.
//  If you use list + [element] then it will append regardless if that element already matches one in the list.
fun main() {
    var t = listOf<Boolean>()

    t = t + true
    println("t + true: $t") // t + true: [true]
    t = t + false
    println("t + false: $t") // t + false: [true, false]
    t = t + false
    println("t + false: $t") // t + false: [true, false, false]
    t = t + true
    println("t + true: $t") // t + true: [true, false, false, true]
    t = t + false
    println("t + false: $t") // t + false: [true, false, false, true, false]
    t = t - false
    println("t - false: $t") // t - false: [true, false, true, false]
    t = t - true
    println("t - true: $t") // t - true: [false, true, false]
    t = t + true
    println("t + true: $t") // t + true: [false, true, false, true]
    t = t + false
    println("t + false: $t") // t + false: [false, true, false, true, false]
    t = t - listOf(true)
    println("t - listOf(true): $t") // t - listOf(true): [false, false, false]
    t = t - listOf(false)
    println("t - listOf(false): $t") // t - listOf(false): []
}

/* Full Output
  t + true: [true]
  t + false: [true, false]
  t + false: [true, false, false]
  t + true: [true, false, false, true]
  t + false: [true, false, false, true, false]
  t - false: [true, false, true, false]
  t - true: [false, true, false]
  t + true: [false, true, false, true]
  t + false: [false, true, false, true, false]
  t - listOf(true): [false, false, false]
  t - listOf(false): []
*/