From: dpb on
Dr Ivan D. Reid wrote:
> On Fri, 22 Jan 2010 13:03:25 GMT, robin <robin_v(a)bigpond.com>
> wrote in <xmh6n.2735$pv.1095(a)news-server.bigpond.net.au>:
>
>> I still use an HP 500C.
>> The Kyocera died years ago, stripping its gears, after a short life.
>
>> That HP 500C is now 15 years old.
>
> I recently revived my [(hp)] HP-21, by buying a pack of two NiMH
> AA batteries at Poundland[1] and slotting them into the battery holder in
> place of the original NiCds. Works fine except the 2 key is a bit reluctant
> to register. I bought it second hand (with a US power-supply switchable
> between 115 and 230 V, and US pins, so I use a UK razor adaptor) when I was
> doing my PhD -- about 1975.
>
> [1] No, don't ask how much they cost...

I've done similar w/ my old HP-97 (the desktop version w/ printer, card
reader, etc.) It all still functions except the rubber rollers for the
paper feed are hard and slick so the paper doesn't feed well any longer.

It's a joy given the size of the keys and display compared to anything
at all newer and advancing eyesight... :) (Although the printing on the
keys is smaller and smaller every day it seems... :( )

--


From: Gordon Sande on
On 2010-01-22 16:34:40 -0400, dpb <none(a)non.net> said:

> Dr Ivan D. Reid wrote:
>> On Fri, 22 Jan 2010 13:03:25 GMT, robin <robin_v(a)bigpond.com>
>> wrote in <xmh6n.2735$pv.1095(a)news-server.bigpond.net.au>:
>>
>>> I still use an HP 500C.
>>> The Kyocera died years ago, stripping its gears, after a short life.
>>
>>> That HP 500C is now 15 years old.
>>
>> I recently revived my [(hp)] HP-21, by buying a pack of two NiMH
>> AA batteries at Poundland[1] and slotting them into the battery holder in
>> place of the original NiCds. Works fine except the 2 key is a bit reluctant
>> to register. I bought it second hand (with a US power-supply switchable
>> between 115 and 230 V, and US pins, so I use a UK razor adaptor) when I was
>> doing my PhD -- about 1975.
>>
>> [1] No, don't ask how much they cost...
>
> I've done similar w/ my old HP-97 (the desktop version w/ printer, card
> reader, etc.) It all still functions except the rubber rollers for the
> paper feed are hard and slick so the paper doesn't feed well any longer.

You can buy a small bottle of numble-numble-alcohol (isoproponol?) which will
remove the glaze and soften the rubber rollers. It used to be in the
do-it-yourself
repair kits for laser printers. Did marvels for an old LaserWriter that
was young
at 10 years of age! If you have an ink cartridge refill outfit locally
they might
have it as a separate item. Otherwise look at the details of laser
printer fixit kits.

> It's a joy given the size of the keys and display compared to anything
> at all newer and advancing eyesight... :) (Although the printing on
> the keys is smaller and smaller every day it seems... :( )


From: Paul Hirose on
"Richard Maine" <nospam(a)see.signature> wrote in message
news:1jckfrv.w6yp2rh7f8q7N%nospam(a)see.signature...
> The arc cosine of -1 is just about the worst case I can think of off
> the
> top of my head in terms of numerical robustness. Hint: look at the
> arc
> cosine of numbers very close to -1. If one is going to use trig
> expressions for things like that, at least use them at decently
> robust
> points. That's independent of the language and the hardware - just
> plain
> numerics.

I hear you. That's why I formerly used 2*acos(0d0) to obtain pi. But
despite the theoretical objection to acos(-1d0), in practice I've
never been able to find a problem. For instance, this program gives
perfect zeros with Silverfrost FTN95 under Windows:

program testpi
implicit none
! double precision real kind
integer, parameter :: dp = selected_real_kind(15)

! original poster's literal
real (kind = dp), parameter :: pi = 3.141592653589793_dp

print '(e10.2, a)', acos(-1.0_dp)-pi, ' = acos(-1)-pi'
print '(e10.2, a)', 2*acos( 0.0_dp)-pi, ' = 2*acos( 0)-pi'
print '(e10.2, a)', 2*asin( 1.0_dp)-pi, ' = 2*asin( 1)-pi'
print '(e10.2, a)', 4*atan( 1.0_dp)-pi, ' = 4*atan( 1)-pi'

end program testpi


My mind is still open on this issue, though. Can anyone demonstrate an
anomalous result with the above program?

The only source code for acos() at hand here is P.J. Plauger, "The
Standard C Library", 1992. His code treats -1 as a special case, and
produces an accurate value for pi. For arguments other than special
cases, he uses polynomials from one of the standard reference books
(Cody and Waite).

Let me make clear that my only claim is that acos(-1d0) has worked
well for *me*, on Windows desktop machines. I put it out there because
calculating pi at runtime from a trig function may be something new to
the original poster. It's embarrassing to admit that I'd been
programming for years before the idea occurred to me.

--
Paul Hirose <jvcmz89uwf(a)earINVALIDthlink.net>
To reply by email remove INVALID

From: Dr Ivan D. Reid on
On Fri, 22 Jan 2010 21:04:01 GMT, Gordon Sande <g.sande(a)worldnet.att.net>
wrote in <2010012217040116807-gsande(a)worldnetattnet>:

>> I've done similar w/ my old HP-97 (the desktop version w/ printer, card
>> reader, etc.) It all still functions except the rubber rollers for the
>> paper feed are hard and slick so the paper doesn't feed well any longer.

> You can buy a small bottle of numble-numble-alcohol (isoproponol?) which will
> remove the glaze and soften the rubber rollers.

Close. Isopropanol, or iso-propyl alcohol. Used as swabs before
injections, etc, etc. I thought you guys called it rubbing alcohol, but my
Chambers suggests rubbing alcohol is methylated spirits (denatured ethanol);
maybe there's a transAtlantic schism there.

--
Ivan Reid, School of Engineering & Design, _____________ CMS Collaboration,
Brunel University. Ivan.Reid@[brunel.ac.uk|cern.ch] Room 40-1-B12, CERN
KotPT -- "for stupidity above and beyond the call of duty".
From: Luka Djigas on
On Fri, 22 Jan 2010 14:34:40 -0600, dpb <none(a)non.net> wrote:

>It's a joy given the size of the keys and display compared to anything
>at all newer and advancing eyesight... :) (Although the printing on the
>keys is smaller and smaller every day it seems... :( )

I have the same problem with cell phones ... (No, 2x2mm in size are
not "large keys").

Soon they'll be giving toothpicks with them, as "human interface
devices".

-- Luka