(TRO) When the last thing a function or procedure does is to
call itself, it is not necessary to retain the calling
environment. This is important when a procedure calls itself
recursively many times for, without tail recursion
optimisation, the environments of earlier invocations would
fill up the memory only to be discarded when (if) the last
call terminated.
Tail recursion optimisation is a special case of
last calloptimisation but it allows the further optimisation that some
arguments may be passed in situ, possibly in
registers. It
allows recursive functions to be compiled into
iterative