On Fri, 19 Oct 2001 09:27:50 -0400
Aaron Sherman <[EMAIL PROTECTED]> wrote:
> > I am implementing a textbook algo in Perl (the textbook has
> > it written in C++) and have realized that if undef was to
> > numericize to NaN instead of 0, there are a lot of uninitialization
> > errors that would g
On Mon, Oct 22, 2001 at 04:27:24PM +0100, Sam Vilain wrote:
> On Fri, 19 Oct 2001 09:27:50 -0400
> Aaron Sherman <[EMAIL PROTECTED]> wrote:
>
> > > I am implementing a textbook algo in Perl (the textbook has
> > > it written in C++) and have realized that if undef was to
> > > numericize to NaN i
Aaron Sherman wrote:
> Let's take this code as an example:
>
> while(<>) {
> $count++;
> $total += substr($_,22,2);
> }
> printf "Average: %.2f\n", $total/$count;
>
> Right now, if my expected numeric column has garbage in it on the
> 400,00
On Mon, 22 Oct 2001 12:18:16 -0400
Aaron Sherman <[EMAIL PROTECTED]> wrote:
> > > $z[0] = 50;
> > > $z[2] = 20;
> > > @x = @y[@z];
> > In your code, should @x contain (@y[50,0,20]) or (@y[50,20]) or
> > (@y[50,undef,20]) ?
> @y[50,undef,20], which in Perl5 is @y[50,0,20].
An arbitrary and
> Aaron Sherman <[EMAIL PROTECTED]> wrote:
> while(<>) {
> $count++;
> $total += substr($_,22,2);
> }
> printf "Average: %.2f\n", $total/$count;
>
>Right now, if my expected numeric column has garbage in it on the
>400,000th line, I treat it as zero a
On Mon, Oct 22, 2001 at 09:39:50AM -0700, Glenn Linderman wrote:
>
> Indeed, you might consider "ignoring garbage" as producing a "meaningful
> result", and in the application you envision, that could be extremely useful.
>
> However, in other applications, the fact that there was garbage on the
On Mon, Oct 22, 2001 at 05:43:58PM +0100, Sam Vilain wrote:
> > More, someone has mentioned the %x{$_}++ feature, which IMHO, MUST
> > continue to work.
>
> What is void plus one?
According to every Perl book I've ever read, 1. I've yet to run into someone
who finds that a difficult concept when
Aaron Sherman wrote:
> I see your point, but going from: "you have to error-check to be
> sure that the average you get is valid" to "you get NaN and like it"
> is a bit steep.
"you get NaN and like it" only happens when you put garbage in... and get garbage
out.
Yes, NaN is garbage. But when
> > More, someone has mentioned the %x{$_}++ feature, which IMHO, MUST
> > continue to work.
>
> What is void plus one?
Can't we utilize the lazy arrays stuff to make all this work.
Out of the box, all entries could default to NaN. But its easy
to write
@a ^= 0;
to change this default.
Aaron Sherman <[EMAIL PROTECTED]> writes:
> On Mon, Oct 22, 2001 at 04:27:24PM +0100, Sam Vilain wrote:
>> On Fri, 19 Oct 2001 09:27:50 -0400
>> Aaron Sherman <[EMAIL PROTECTED]> wrote:
>>
>> > > I am implementing a textbook algo in Perl (the textbook has
>> > > it written in C++) and have reali
On Mon, Oct 22, 2001 at 07:39:44PM +0100, Piers Cawley wrote:
> Yeah, but it's correct. If you extract something and get garbage then
> you're going to screw your average up. Admittedly, in 400,000 lines,
> it's unlikely to shift the average by much, but it will shift it.
No, I'm interpreting u
On Mon, Oct 22, 2001 at 11:30:01AM -0700, David Whipp wrote:
> > > More, someone has mentioned the %x{$_}++ feature, which IMHO, MUST
> > > continue to work.
> >
> > What is void plus one?
>
> Can't we utilize the lazy arrays stuff to make all this work.
> Out of the box, all entries could defau
Aaron Sherman wrote
> On Mon, Oct 22, 2001 at 11:30:01AM -0700, David Whipp wrote:
> > > > More, someone has mentioned the %x{$_}++ feature, which
> IMHO, MUST
> > > > continue to work.
> > >
> > > What is void plus one?
> >
> > Can't we utilize the lazy arrays stuff to make all this work.
> >
Aaron Sherman <[EMAIL PROTECTED]> writes:
> On Mon, Oct 22, 2001 at 07:39:44PM +0100, Piers Cawley wrote:
>
>> Yeah, but it's correct. If you extract something and get garbage then
>> you're going to screw your average up. Admittedly, in 400,000 lines,
>> it's unlikely to shift the average by mu
Aaron Sherman <[EMAIL PROTECTED]> writes:
> On Mon, Oct 22, 2001 at 11:30:01AM -0700, David Whipp wrote:
>> > > More, someone has mentioned the %x{$_}++ feature, which IMHO, MUST
>> > > continue to work.
>> >
>> > What is void plus one?
>>
>> Can't we utilize the lazy arrays stuff to make all t
On Mon, Oct 22, 2001 at 08:25:21PM +0100, Piers Cawley wrote:
> > What REALLY worries me is that values that seem to be numbers, but are
> > in fact garbage ARE going to screw my average up. I dare Perl6 to fix
> > that for me.
>
> It's not going to. Getting NaN as a result in this context shoul
On Mon, Oct 22, 2001 at 12:23:34PM -0700, David Whipp wrote:
> Aaron Sherman wrote
> >
> > my @a;
> > @a ^= 0;
> > print @a
> >
> > Are you saying that this should print an infinite number of zeros?
> >
>
> Quoting Larry on this subject (apocalypse 3, bottom of page 3): "I
> can th
> > Aaron Sherman wrote
> Larry's hubris notwithstanding, I'd like to suggest that
> "more", in this
> case means "no, it prints nothing".
>
> This *must* be true, as you don't want:
>
> @a ^+ @b
>
> to always return an infinite list. You want it to produce a list with
> (as a3 suggested
On Mon, Oct 22, 2001 at 01:36:02PM -0700, David Whipp wrote:
> OK, now we've got this resolved, I'd like to return the focus
> back to the original point.
>
> @x ^= 0;
> @x[5]++;
>
> does not have problems with NaNs; and does not generate a warning
> with -w.
Someone's missing some
On Mon, Oct 22, 2001 at 04:21:32PM -0400, Aaron Sherman wrote:
> On Mon, Oct 22, 2001 at 08:25:21PM +0100, Piers Cawley wrote:
>
> > > What REALLY worries me is that values that seem to be numbers, but are
> > > in fact garbage ARE going to screw my average up. I dare Perl6 to fix
> > > that for
Okay, in the (probably forlorn) hope of beating this subject to death,
let me offer a possible (post-A3/E3) position on NaN.
NaN is dead.
Except perhaps under a C pragma of some kind, in which case it
would be a proper IEEE NaN.
C with numerify to zero (it always has; and we always intended
th
[Oops, I fired off too-early a draft. Here's the full thing...]
Okay, in the (probably forlorn) hope of finally Beating This Subject To Death,
let me offer a (possible) new position on NaN.
NaN is dead. It's not pinin'! It's passed on! This value is no more! It
has ceased to be! It's expired a
On Tue, Oct 23, 2001 at 07:30:00AM +1000, Damian Conway wrote:
> To check for numericity of input, you'll write:
>
> $number = +<$fh>
> until defined $number;
>
> If you ignore the definedness, the C will just promote to zero
> in numeric contexts.
I'm confused. By the
> > To check for numericity of input, you'll write:
> >
> > $number = +<$fh>
> > until defined $number;
> >
> > If you ignore the definedness, the C will just promote to zero
> > in numeric contexts.
>
> I'm confused. By the time $number see
Aaron Sherman wrote:
> Someone's missing something, and I sure hope it's not me. Let me write
> a code sample here:
>
> sub incrind (@ary, $ind) {
> @ary[$ind]++
> }
>
> Are you suggesting that by adding in "@ary ^= 0", like so:
>
> sub incrind (@ary, $ind) {
>
Hufgo suggested:
> :Have I missed anything?
>
> Code, and docs, for ieee.pm. Other than that, it looks good to me. :)
Ah, but that's a SMoP, left as an exercise to the reader.
;-)
Damian
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