[sf-perl] Perl 6 Informal Study Session: 1pm Sunday April 22nd, at the Oakland Museum

yary not.com at gmail.com
Sat Apr 28 17:52:56 PDT 2018


I guess it isn't a bug, overflow error is better than Inf, I just assumed
that 4 ^ (4 ^ (4 ^ 4) ) would be still small enough to be in a Num. But it
is one of those numbers whose digit count is roughly the universe's atom
count.

Fast growing functions are fun, every time I read about them, I spend an
hour plus in math site & wikipedia rabbit holes reading things I know
nothing about.

See you tomorrow at the study session!

-y

On Sat, Apr 28, 2018 at 9:04 PM, Joseph Brenner <doomvox at gmail.com> wrote:

> I'm not sure where you think the bug is there, Yary.   Do you get that
> this is supposed to be a function that grows insanely fast?   It works
> like:
>
> 2 ^ 2
> 3 ^ 3 ^ 3
> 4 ^ 4 ^ 4 ^ 4
> 5 ^ 5 ^ 5 ^ 5 ^ 5
> 6 ^ 6 ^ 6 ^ 6 ^ 6 ^ 6
>
> (Heinlein used to say that that was the actual "number of the beast".)
>
> The emacs calc package agrees on the value for 3.
> I'm not sure if it'd call the value for 4 infinity, I wasn't willing
> to wait for it to finish.
>
> In perl6 I might do it like this:
>
> for (1 .. 4) -> $i {  # line 7
>     my $r = $i;
>     for (2 .. $i) {
>       $r = $i ** $r;   # line 10
>      }
>    print "$i: $r\n";  # line 12
>  }
>
>
> Running that it behaves similarly, throwing an overflow error.   It's
> funny that it reports three line numbers, though:
>
> 1: 1
> 2: 4
> 3: 7625597484987
> Numeric overflow
>   in block  at /home/doom/End/Cave/Eye/bin/davids_insane_func.pl6 line 10
>   in block <unit> at /home/doom/End/Cave/Eye/bin/davids_insane_func.pl6
> line 7
>
> Actually thrown at:
>   in block <unit> at /home/doom/End/Cave/Eye/bin/davids_insane_func.pl6
> line 12
>
>
>
>
> On Sun, Apr 22, 2018 at 10:30 PM, yary <not.com at gmail.com> wrote:
> >
> >
> > -y
> >
> > On Sun, Apr 22, 2018 at 10:09 PM, David Christensen
> > <dpchrist at holgerdanske.com> wrote:
> >>
> >>
> >>
> >> print join ' ', $_, f($_), "\n" for 1 .. 4;
> >>
> >>
> >> 2018-04-22 19:03:30 dpchrist at vstretch ~/sandbox/perl
> >> $ perl6 growth
> >> 1 1
> >> 2 4
> >> 3 7625597484987
> >> Numeric overflow
> >>   in sub f at growth line 6
> >>   in block <unit> at growth line 11
> >>
> >> Actually thrown at:
> >>   in block <unit> at growth line 11
> >
> >
> > That looks like a bug- have you reported it? Not that I know where to
> > report/check for bugs...
> >
> > --
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