Front page | perl.perl6.language |
Postings from October 2008
On Sun, Oct 05, 2008 at 08:19:42PM -0700, Jon Lang wrote: : <larry@cvs.perl.org> wrote: : > Log: : > Add missing series operator, mostly for readability. : : Is there a way for the continuing function to access its index as well : as, or instead of, the values of one or more preceding terms? And/or : to access elements by counting forward from the start rather than : backward from the end? That's what the other message was about. @_ represents the entire list generated so far, so you can look at its length or index it from the begining. Not guaranteed to be as efficient though. : There is a mathematical technique whereby any series that takes the : form of "F(n) = A*F(n-1) + B*F(n-2) + C*F(n-3)" can be reformulated as : a function of n, A, B, C, F(0), F(1), and F(2). (And it is not : limited to three terms; it can be as few as one or as many as n-1 - : although it has to be the same number for every calculated term in the : series.) For the Fibonacci series, it's something like: : : F(n) = (pow((sqrt(5) + 1)/2, n) + pow((sqrt(5) - 1)/2, n))/sqrt(5) : : ...or something to that effect. It would be nice if the programmer : were given the tools to do this sort of thing explicitly instead of : having to rely on the optimizer to know how to do this implicitly. Um, I don't understand what you're asking for. Explicit solutions are always available... LarryThread Previous | Thread Next