Problem Statement
What is tail recursion in Kotlin and how does the tailrec modifier optimize recursive functions?
Explanation
Tail recursion occurs when a recursive call is the last operation in a function with no further processing after it returns, and Kotlin optimizes tail-recursive functions marked with tailrec modifier by converting them into iterative loops avoiding stack overflow. The compiler transforms tail-recursive functions into loops reusing the same stack frame rather than creating new frames for each recursive call, enabling safe recursive implementations of algorithms that would otherwise overflow the stack.
To use tailrec, ensure the recursive call is truly the last operation with no further computation after it, not followed by any operations like addition or method calls. The function must call itself directly not through another function or lambda, and the compiler warns you if tailrec cannot be applied helping you identify non-tail-recursive patterns.
Use tail recursion for algorithms naturally expressed recursively like factorial, fibonacci, or list processing where iteration would be less clear, but be aware that not all recursive algorithms can be expressed in tail-recursive form. Understanding tail recursion helps write efficient recursive code without stack limitations while maintaining functional programming style.