invalid floating point value

[Dik T. Winter]

Re: invalid floating point value

In article <cjh6e8$7j3$5@s unnews.cern.ch> Dan.Pop@cern.ch (Dan Pop) writes:[color=blue]
> In <I4uuuo.DM5@cwi .nl> "Dik T. Winter" <Dik.Winter@cwi .nl> writes:[color=green]
> >In article <cjgtn1$gh9$4@s unnews.cern.ch> Dan.Pop@cern.ch (Dan Pop) writes:[color=darkred]
> > > The OP was looking for a bit pattern that could be reliably used
> > > *everywhere* as not corresponding to any floating point value.[/color]
> >
> >Not entirely true. He was asking for a value that could be used to
> >distinguish non-initialized valiables from initialized vairables
> >(note the mention of -999.0 commonly being used). A value that is
> >never generated by the processor could serve very well for such a
> >purpose.[/color]
>
> How do you store such a "value" in a variable in the first place?[/color]

You are dense. Obviously I meant "never generated by the floating-point
part of the processor".
--
dik t. winter, cwi, kruislaan 413, 1098 sj amsterdam, nederland, +31205924131
home: bovenover 215, 1025 jn amsterdam, nederland; http://www.cwi.nl/~dik/

[Dan Pop]

Re: invalid floating point value

In <I4wn0F.Dxr@cwi .nl> "Dik T. Winter" <Dik.Winter@cwi .nl> writes:
[color=blue]
>In article <cjje98$r25$3@s unnews.cern.ch> Dan.Pop@cern.ch (Dan Pop) writes:[color=green]
> > In <I4vL47.Gyx@cwi .nl> "Dik T. Winter" <Dik.Winter@cwi .nl> writes:
> >[color=darkred]
> > >In article <cjh6e8$7j3$5@s unnews.cern.ch> Dan.Pop@cern.ch (Dan Pop) writes:
> > > > In <I4uuuo.DM5@cwi .nl> "Dik T. Winter" <Dik.Winter@cwi .nl> writes:
> > > > >In article <cjgtn1$gh9$4@s unnews.cern.ch> Dan.Pop@cern.ch (Dan Pop) writes:
> > > > > > The OP was looking for a bit pattern that could be reliably used
> > > > > > *everywhere* as not corresponding to any floating point value.
> > > > >
> > > > >Not entirely true. He was asking for a value that could be used to
> > > > >distinguish non-initialized valiables from initialized vairables
> > > > >(note the mention of -999.0 commonly being used). A value that is
> > > > >never generated by the processor could serve very well for such a
> > > > >purpose.
> > > >
> > > > How do you store such a "value" in a variable in the first place?
> > >
> > >You are dense.[/color]
> >
> > Nope.
> >[color=darkred]
> > >Obviously I meant "never generated by the floating-point part of the
> > >processor".[/color]
> >
> > And this is how I interpreted it. But you called it a "value" and
> > objected to my treating it as a bit pattern. So, please make up your
> > mind.[/color]
>
>I use "value" and "bit pattern" here interchangably. It was *not*
>your use of "bit pattern" I objected to. It was your use of
>"not corresponding to any floating point value" I objected to.[/color]

My usage was consistent to the OP's:

A C double can be aliased by an array of unsigned char, to which
any desired byte pattern may be written. Is there any somewhat
portable way of assigning a byte pattern such that the result
will, with very high probability, _not_ count as a valid double?

And, unless I'm missing something, you've been unable to produce such a
bit pattern, so your contributions to this thread have consisted of pure
noise...

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de
Currently looking for a job in the European Union

[Dik T. Winter]

Re: invalid floating point value

In article <cjjilj$9q1$1@s unnews.cern.ch> Dan.Pop@cern.ch (Dan Pop) writes:[color=blue]
> In <I4wn0F.Dxr@cwi .nl> "Dik T. Winter" <Dik.Winter@cwi .nl> writes:[/color]
....[color=blue][color=green]
> >I use "value" and "bit pattern" here interchangably. It was *not*
> >your use of "bit pattern" I objected to. It was your use of
> >"not corresponding to any floating point value" I objected to.[/color]
>
> My usage was consistent to the OP's:
>
> A C double can be aliased by an array of unsigned char, to which
> any desired byte pattern may be written. Is there any somewhat
> portable way of assigning a byte pattern such that the result
> will, with very high probability, _not_ count as a valid double?
>
> And, unless I'm missing something, you've been unable to produce such a
> bit pattern, so your contributions to this thread have consisted of pure
> noise...[/color]

The OP continues with:
I ask because I'm in search of a mechanism for flagging "missing
values" in an array of doubles. I'm aware that the "best" (fully
portable) way probably involves setting up an ancillary array, or
making the basic data-type not a straight double but a struct of
some sort. But in context this would be a royal pain. One
common solution is to flag "missing" with a specific value such
as -999.0. I'm wondering if that can be improved upon without
resorting to a wider data type.
a bit pattern not generated by the floating point processor serves his
purpose very well.
--
dik t. winter, cwi, kruislaan 413, 1098 sj amsterdam, nederland, +31205924131
home: bovenover 215, 1025 jn amsterdam, nederland; http://www.cwi.nl/~dik/

[Dan Pop]

Re: invalid floating point value

In <I4wqDJ.66u@cwi .nl> "Dik T. Winter" <Dik.Winter@cwi .nl> writes:
[color=blue]
>In article <cjjilj$9q1$1@s unnews.cern.ch> Dan.Pop@cern.ch (Dan Pop) writes:[color=green]
> > In <I4wn0F.Dxr@cwi .nl> "Dik T. Winter" <Dik.Winter@cwi .nl> writes:[/color]
>...[color=green][color=darkred]
> > >I use "value" and "bit pattern" here interchangably. It was *not*
> > >your use of "bit pattern" I objected to. It was your use of
> > >"not corresponding to any floating point value" I objected to.[/color]
> >
> > My usage was consistent to the OP's:
> >
> > A C double can be aliased by an array of unsigned char, to which
> > any desired byte pattern may be written. Is there any somewhat
> > portable way of assigning a byte pattern such that the result
> > will, with very high probability, _not_ count as a valid double?
> >
> > And, unless I'm missing something, you've been unable to produce such a
> > bit pattern, so your contributions to this thread have consisted of pure
> > noise...[/color]
>
>The OP continues with:
> I ask because I'm in search of a mechanism for flagging "missing
> values" in an array of doubles. I'm aware that the "best" (fully
> portable) way probably involves setting up an ancillary array, or
> making the basic data-type not a straight double but a struct of
> some sort. But in context this would be a royal pain. One
> common solution is to flag "missing" with a specific value such
> as -999.0. I'm wondering if that can be improved upon without
> resorting to a wider data type.
>a bit pattern not generated by the floating point processor serves his
>purpose very well.[/color]

But you still have been unable to produce one, so you're merely generating
more noise.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de
Currently looking for a job in the European Union

[Dik T. Winter]

Re: invalid floating point value

In article <cjjn0n$2sj$2@s unnews.cern.ch> Dan.Pop@cern.ch (Dan Pop) writes:[color=blue]
> In <I4wqDJ.66u@cwi .nl> "Dik T. Winter" <Dik.Winter@cwi .nl> writes:[/color]
....[color=blue][color=green]
> >The OP continues with:
> > I ask because I'm in search of a mechanism for flagging "missing
> > values" in an array of doubles. I'm aware that the "best" (fully
> > portable) way probably involves setting up an ancillary array, or
> > making the basic data-type not a straight double but a struct of
> > some sort. But in context this would be a royal pain. One
> > common solution is to flag "missing" with a specific value such
> > as -999.0. I'm wondering if that can be improved upon without
> > resorting to a wider data type.
> >a bit pattern not generated by the floating point processor serves his
> >purpose very well.[/color]
>
> But you still have been unable to produce one, so you're merely generating
> more noise.[/color]

Darn. I have written that I know such patterns exist for the PDP 11, Vax,
Gould, Cray 1, CDC Cyber, and I know of only two processors for which they
definitely do not exist. So I have no idea what you are intending to say
here.
--
dik t. winter, cwi, kruislaan 413, 1098 sj amsterdam, nederland, +31205924131
home: bovenover 215, 1025 jn amsterdam, nederland; http://www.cwi.nl/~dik/

[Suzie]

Re: invalid floating point value

> So I have no idea what you are intending to say here.

He's just being an asshole know-it-all, as usual.

[Dan Pop]

Re: invalid floating point value

In <I4wtDo.LFs@cwi .nl> "Dik T. Winter" <Dik.Winter@cwi .nl> writes:
[color=blue]
>In article <cjjn0n$2sj$2@s unnews.cern.ch> Dan.Pop@cern.ch (Dan Pop) writes:[color=green]
> > In <I4wqDJ.66u@cwi .nl> "Dik T. Winter" <Dik.Winter@cwi .nl> writes:[/color]
>...[color=green][color=darkred]
> > >The OP continues with:
> > > I ask because I'm in search of a mechanism for flagging "missing
> > > values" in an array of doubles. I'm aware that the "best" (fully
> > > portable) way probably involves setting up an ancillary array, or
> > > making the basic data-type not a straight double but a struct of
> > > some sort. But in context this would be a royal pain. One
> > > common solution is to flag "missing" with a specific value such
> > > as -999.0. I'm wondering if that can be improved upon without
> > > resorting to a wider data type.
> > >a bit pattern not generated by the floating point processor serves his
> > >purpose very well.[/color]
> >
> > But you still have been unable to produce one, so you're merely generating
> > more noise.[/color]
>
>Darn. I have written that I know such patterns exist for the PDP 11, Vax,
>Gould, Cray 1, CDC Cyber, and I know of only two processors for which they
>definitely do not exist. So I have no idea what you are intending to say
>here.[/color]

One such bit pattern that works *portably*. Which is what the OS was
asking about.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Dan.Pop@ifh.de
Currently looking for a job in the European Union