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tim.... wrote:

"Chris Tolley" (ukonline really) wrote in message
.. .
tim.... wrote:

"John Levine" wrote in message
...
Another bunch of rather less intelligent people insist that there was
a year zero, ...

Actually, there was a year zero but for reasons that are self-evident
if you know what happened then, there's been a huge cover-up ever
since. You're not supposed to know that. Despite the disinformation
that it was a rather ordinary year in Augustinian Rome, it's when
people first realized that the al~~~r~~~!~

Well it's flipping well all made up based upon an event that didn't
happen,
so why does it matter?

What event would that be?

A "virgin birth" (as I understand)

If you are referring to the birth of Jesus of Nazareth, then there is
very little doubt (except among those who doubt everything as a matter
of policy) that the event happened.

Either way, that is not the zero point of the calendar, though it is
related to it.
--
http://gallery120232.fotopic.net/p9632950.html
(43 060 at London Kings Cross, 1982)

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In uk.transport.london message 39bb4a9f-1c49-4a8b-acbf-75f9835d6af9@j25
g2000yqa.googlegroups.com, Sat, 23 Oct 2010 07:28:23, MIG
posted:

Another bunch of rather less intelligent people insist that there was
a year zero, because "zero is a positive integer". Zero might
represent a point in time when zero years have passed. A year later,
one year has passed. This would be the first year, and in any normal
counting system it would be referred to as year one, ie the number of
years that have passed when it is complete.


In IEEE-754 floating-point "single" and "Double" number formats. there
is both a +zero and a -zero. They have the same value and compare
equal, but they are distinguishable, even in languages that do not offer
access to the bit patterns as such.

Astronomer's notation calls 1 BC the year zero; it numbers years in the
usual arithmetic fashion, and agrees with the common notation for all of
AD.

--
(c) John Stockton, nr London, UK. Turnpike v6.05.
Website http://www.merlyn.demon.co.uk/ - w. FAQish topics, links, acronyms
PAS EXE etc. : http://www.merlyn.demon.co.uk/programs/ - see in 00index.htm
Dates - miscdate.htm estrdate.htm js-dates.htm pas-time.htm critdate.htm etc.

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On 24 Oct, 20:21, Dr J R Stockton
wrote:
In uk.transport.london message 39bb4a9f-1c49-4a8b-acbf-75f9835d6af9@j25
g2000yqa.googlegroups.com, Sat, 23 Oct 2010 07:28:23, MIG
posted:

Another bunch of rather less intelligent people insist that there was
a year zero, because "zero is a positive integer". *Zero might
represent a point in time when zero years have passed. *A year later,
one year has passed. *This would be the first year, and in any normal
counting system it would be referred to as year one, ie the number of
years that have passed when it is complete.

In IEEE-754 floating-point "single" and "Double" number formats. there
is both a +zero and a -zero. *They have the same value and compare
equal, but they are distinguishable, even in languages that do not offer
access to the bit patterns as such.

I don't think they were using those formats when the calendar was set
up.


Astronomer's notation calls 1 BC the year zero; it numbers years in the
usual arithmetic fashion, and agrees with the common notation for all of
AD.

That's kind of consistent in that when that year was complete, ie at
the same point zero when year 1 starts, zero years had passed beyond
the point zero where we start counting positively.

But one still starts counting from point zero, not from point minus
one, where "year zero" (or one BC) starts.

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In article id,
Dr J R Stockton wrote:

In IEEE-754 floating-point "single" and "Double" number formats. there
is both a +zero and a -zero. They have the same value and compare
equal, ...

As do ones-complement integers (which I assume the IEEE-754 formats use
in some form)...

... but they are distinguishable, even in languages that do not offer
access to the bit patterns as such.

.... though I don't know of any higher-level languages that let you
distinguish between +0 and -0 integers even on hardware that supports
the distinction. (And FWIW the TCP/IP suite uses ones-complement
arithmetic in its checksum calculations.)

Sam

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Sam Wilson wrote


... but they are distinguishable, even in languages that do not
offer
access to the bit patterns as such.

... though I don't know of any higher-level languages that let you
distinguish between +0 and -0 integers even on hardware that supports

the distinction. (And FWIW the TCP/IP suite uses ones-complement
arithmetic in its checksum calculations.)

Fortran on the Univac/Unisys 1100 series (which used one-complement
single and double integers and indeed floating point). IIRC the CDC
6600/7600 was the same in providing functions for bit-wise AND, OR, XOR
and NOT.

--
Mike D

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In uk.transport.london message
ernal-september.org, Mon, 25 Oct 2010 17:36:10, Sam Wilson
posted:

In article id,
Dr J R Stockton wrote:

In IEEE-754 floating-point "single" and "Double" number formats. there
is both a +zero and a -zero. They have the same value and compare
equal, ...

As do ones-complement integers (which I assume the IEEE-754 formats use
in some form)...

Never assume when you can Wiki ! They encode the unsigned part of
Numbers as mantissa and exponent, and put a sign bit in front.


... but they are distinguishable, even in languages that do not offer
access to the bit patterns as such.

... though I don't know of any higher-level languages that let you
distinguish between +0 and -0 integers even on hardware that supports
the distinction.

In JavaScript, where Numbers are Doubles, one does it by taking the
reciprocal. Plus infinity and minus infinity are easily told apart.
The internal sign of a Number X (that is not NaN) can be determined by
comparing X + 1/X with a zero. Min(Abs(X+1/X)) = 2, at least for real
numbers.

--
(c) John Stockton, nr London, UK. Turnpike v6.05 MIME.
Web http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms and links;
Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.

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On Tue, 26 Oct 2010, Michael R N Dolbear wrote:

Sam Wilson wrote

... but they are distinguishable, even in languages that do not offer
access to the bit patterns as such.

... though I don't know of any higher-level languages that let you
distinguish between +0 and -0 integers even on hardware that supports
the distinction. (And FWIW the TCP/IP suite uses ones-complement
arithmetic in its checksum calculations.)

Fortran on the Univac/Unisys 1100 series (which used one-complement
single and double integers and indeed floating point). IIRC the CDC
6600/7600 was the same in providing functions for bit-wise AND, OR, XOR
and NOT.

I wandered off this thread early on, as i'm not that interested in the
machinations of Oyster. I return to find that some truly superb drifting
has been done. Well done, chaps, you guys could give the Tokyo mob a run
for their money!

tom

--
Perfection is achieved, not when there is nothing more to add, but when
there is nothing left to take away. -- Antoine de Saint-Exupery

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In article 01cb7539$ac03b1a0$LocalHost@default,
"Michael R N Dolbear" wrote:

Sam Wilson wrote


... but they are distinguishable, even in languages that do not
offer
access to the bit patterns as such.

... though I don't know of any higher-level languages that let you
distinguish between +0 and -0 integers even on hardware that supports

the distinction. (And FWIW the TCP/IP suite uses ones-complement
arithmetic in its checksum calculations.)

Fortran on the Univac/Unisys 1100 series (which used one-complement
single and double integers and indeed floating point). ...

So are you saying you could write IF (I .EQ. -0) and have it behave
differently from (I .EQ. 0) or (I .EQ. +0), or just that you could do
bitwise ops?

... IIRC the CDC
6600/7600 was the same in providing functions for bit-wise AND, OR, XOR
and NOT.

Sam

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In article id,
Dr J R Stockton wrote:

In uk.transport.london message
ernal-september.org, Mon, 25 Oct 2010 17:36:10, Sam Wilson
posted:

In article id,
Dr J R Stockton wrote:

In IEEE-754 floating-point "single" and "Double" number formats. there
is both a +zero and a -zero. They have the same value and compare
equal, ...

As do ones-complement integers (which I assume the IEEE-754 formats use
in some form)...

Never assume when you can Wiki ! They encode the unsigned part of
Numbers as mantissa and exponent, and put a sign bit in front.

Good point! Sign+magnitude[+exponent] rather than ones' complement.

... but they are distinguishable, even in languages that do not offer
access to the bit patterns as such.

... though I don't know of any higher-level languages that let you
distinguish between +0 and -0 integers even on hardware that supports
the distinction.

In JavaScript, where Numbers are Doubles, one does it by taking the
reciprocal. Plus infinity and minus infinity are easily told apart.
The internal sign of a Number X (that is not NaN) can be determined by
comparing X + 1/X with a zero. Min(Abs(X+1/X)) = 2, at least for real
numbers.

Yeah, but you can't say something like

if (result == +0)
{
...
}
else if (result == -0)
{
...
}

can you?

Sam

and have it operate differently from

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Sam Wilson wrote
"Michael R N Dolbear" wrote:

... though I don't know of any higher-level languages that let
you
distinguish between +0 and -0 integers even on hardware that
supports
the distinction. (And FWIW the TCP/IP suite uses ones-complement

arithmetic in its checksum calculations.)

Fortran on the Univac/Unisys 1100 series (which used one-complement
single and double integers and indeed floating point). ...

So are you saying you could write IF (I .EQ. -0) and have it behave
differently from (I .EQ. 0) or (I .EQ. +0), or just that you could do

bitwise ops?

There were lots of ways of doing it but I would have used something
like

IF (I .EQ. 0 .AND AND(I,1) .NE. 0)

IF (I .EQ. -0) however (and any other operation using only Standard
Fortran operations and functions) has to give the same result
irrespective of the underlying hardware or be in violation of Standard
Fortran.. Thus when one looked at the compiler generated code there was
an occasional "force -0 to +0" sequence.

In memory of a great mainframe

http://www.fourmilab.ch/documents/univac/minuszero.html

--
Mike D