I did not know, that lambdas are allocated on the heap. I have a few questions now:
How does this affect using fibers? (And how do fibers work better in that case?) The unrolling you mentioned. Would same not be possible for the naive-but-not-tail-recursive version? Is the idea, that the continuation tail recursive version does work better, because the compiler is somehow able to optimize it better? If so, why? I am asking, because I once had the same kind of problem and then read, that instead of growing stack levels, I am growing the continuation, so not winning anything. But perhaps that was wrong and I should have gone for the continuation solution. I would like to be able to make an educated decision when next meeting such a problem. Best regards, Zelphir On 12/15/21 1:59 PM, Stefan Israelsson Tampe wrote: > I believe that the lambda closures will be allocated from the heap and hence > this procedure will > be perfect if you are using fibers.. Also the compiler can do magic if it > want's and unroll > and untangle a few iterations, so it can be very fast as well.My point is that > the named let > is such a nice looping construct (try to do this with a for loop in java). I > use it all the time > and only sometimes I need to move to even more advanced constructs like > letrec. > > On Wed, Dec 15, 2021 at 10:38 AM Zelphir Kaltstahl <zelphirkaltst...@posteo.de > <mailto:zelphirkaltst...@posteo.de>> wrote: > > Hello Stefan! > > This translates a recursive tree function into a tail recursive function. > However, in this case, I am not sure it is really worth doing, in > comparison to > the naive (+ first-branch other-branch) solution. The reason is, that > instead of > a call stack for multiple branches, you are only moving that stuff into a > longer > and longer continuation, which will be on the stack in each recursive > call. > > However, I think you or other people on the list probably know more about > this > than I do and about how the approaches compare in terms of memory and > time. > Maybe the stack frames are more in size than the memory consumed by the > overhead > of the continuation, or the other way around. > > Regards, > Zelphir > > On 12/15/21 12:44 AM, Stefan Israelsson Tampe wrote: > > Maybe you think the below program is trivial, but I adore named let's so > > much that I just cannot fathom that when people go functional they > totally > > miss this beauty > > > > > > (define (count tree) > > > > ;; s = total sum up to now > > > > ;; t = tree of the type (car = child . cdr = siblings) > > > > ;; cont is the continuation, (cont 10) will continue > > > > ;; the calculation with the sum=10 see how we initiate > > > > ;; with a continuation that evaluates returns it's argument > > > > > > (let loop ((s 0) (t tree) (cont (lambda (s) s))) > > > > (if (pair? t) > > > > (loop s (car t) (lambda (s) (loop s (cdr t) cont))) > > > > (cont (if (number? t) t 0)))) > > -- > repositories: https://notabug.org/ZelphirKaltstahl > <https://notabug.org/ZelphirKaltstahl> > -- repositories: https://notabug.org/ZelphirKaltstahl
