`tailrec` asks the compiler to optimize tail recursion into a loop (no growing call stack). It works only for direct self-recursion where the recursive call is the last operation (tail position). If the function is not truly tail-recursive, the compiler will not apply the optimization.
Advanced answer
Deep dive
Expanding on the short answer — what usually matters in practice:
Explain the "why", not just the "what" (intuition + consequences).
Trade-offs: what you gain/lose (time, memory, complexity, risk).
Edge cases: empty inputs, large inputs, invalid inputs, concurrency.
Examples
A tiny example (an explanation template):
// Example: discuss trade-offs for "`tailrec`:-what-does-it-do-and-when-can-kotlin-o"
function explain() {
// Start from the core idea:
// `tailrec` asks the compiler to optimize tail recursion into a loop (no growing call stack)
}
Common pitfalls
Too generic: no concrete trade-offs or examples.
Mixing average-case and worst-case (e.g., complexity).