järelkäändest

Järelkäändest, also known as a tail recurse or trailing recursion, is a programming concept related to recursion. It occurs when a function calls itself as the very last operation it performs. This means that after the recursive call returns its value, the function doesn't need to do any further work with that value.

The significance of tail recursion lies in its potential for optimization by compilers and interpreters. Because no further computation is required after the recursive call, the system can reuse the current stack frame instead of allocating a new one. This process is known as tail-call optimization (TCO).

When TCO is applied, tail-recursive functions can be executed with the same memory efficiency as iterative loops, preventing stack overflow errors that can occur with deep recursion in languages that do not implement TCO. This makes tail recursion a valuable technique for writing efficient recursive algorithms, particularly in functional programming languages where recursion is frequently used.

To be considered a tail call, the recursive call must be the absolute last action in the function. Any operation performed after the recursive call, even a simple addition or function return, prevents it from being a tail call and thus from being optimized by TCO. Languages like Scheme, Haskell, and Scala are known for their robust support for tail-call optimization.