Another tail recursion example

Ian Kelly ian.g.kelly at
Wed Jul 29 00:06:23 CEST 2015

On Jul 28, 2015 1:36 PM, "Paul Rubin" < at nospam.invalid> wrote:
> Paul Rubin < at nospam.invalid> writes:
> > Chris Angelico was asking for examples of tail recursion that didn't
> > have obvious looping equivalents.  Here's an Euler problem solution
> > using memoization and (except that Python doesn't implement it) tail
> > recursion with an accumulator.
> Actually that's wrong, it's not really tail recursive because of the
> addition in the memo combinator, whoops ;-).

Not just the addition, but the setdefault call as well. Without the
addition that call could be tail-call optimized, but that's not the
recursive call; the call to func is.
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