bug#35608: 26.2; Calc temperature conversions

bug#35608: 26.2; Calc temperature conversions

[Harris, Bill]

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I started Emacs from Cygwin with

$ /cygdrive/c/emacs/emacs-26.2-x86_64/bin/runemacs.exe  -Q

I typed C-x * * to start Calc.

I entered '10 degC' and then

u c degF

I got 18, not the expected 50.

From *Calc Trail*:

Emacs Calculator Trail
alg' 10 * degC
cvun 18. * degF



In GNU Emacs 26.2 (build 1, x86_64-w64-mingw32)
of 2019-04-13 built on CIRROCUMULUS
Repository revision: fd1b34bfba8f3f6298df47c8e10b61530426f749
Windowing system distributor 'Microsoft Corp.', version 10.0.17134
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Defining kbd macro...
C-x *  (Type ? for a list of Calc options)
Welcome to the GNU Emacs Calculator!  Press '?' or 'h' for help, 'q' to quit
Working...
Building units table...done
Quit [4 times]
Configured using:
'configure --without-dbus --host=x86_64-w64-mingw32
--without-compress-install 'CFLAGS=-O2 -static -g3''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY ACL GNUTLS LIBXML2 ZLIB
TOOLKIT_SCROLL_BARS THREADS LCMS2

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: cp1252

Major mode: Lisp Interaction

Minor modes in effect:
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Load-path shadows:
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Memory information:
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bug#35608: 26.2; Calc temperature conversions

[Mauro Aranda]

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tags 35608 notabug
quit

"Harris, Bill" <wsharris@snopud.com> writes:

> I entered '10 degC' and then
> u c degF
> I got 18, not the expected 50.

Hello.

That's because ‘u c’ treats temperature units as relative, and not as
absolute.  The result you got means that a change of 10 degrees Celsius
equals to a change of 18 degrees Fahrenheit.

You need to use ‘u t’ (calc-convert-temperature) to convert an absolute
temperature from one scale to another.  With that command, you'll get
the expected 50 degF.

Best regards,
Mauro.

>

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bug#35608: 26.2; Calc temperature conversions

[Harris, Bill]

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Thank you, Mauro.  I thought it gave absolute temperatures in previous versions (26.1, for example), but I just checked on version 25.1, and it, too, does as you say.

Bill

From: Mauro Aranda <maurooaranda@gmail.com>
Sent: Monday, May 6, 2019 2:19 PM
To: Harris, Bill <wsharris@snopud.com>
Cc: 35608@debbugs.gnu.org
Subject: Re: bug#35608: 26.2; Calc temperature conversions

CAUTION: THIS EMAIL IS FROM AN EXTERNAL SENDER.
Do not click on links or open attachments if the sender is unknown or the email is suspect.
________________________________
tags 35608 notabug
quit

"Harris, Bill" <wsharris@snopud.com<mailto:wsharris@snopud.com>> writes:

> I entered '10 degC' and then
> u c degF
> I got 18, not the expected 50.

Hello.

That's because ‘u c’ treats temperature units as relative, and not as
absolute.  The result you got means that a change of 10 degrees Celsius
equals to a change of 18 degrees Fahrenheit.

You need to use ‘u t’ (calc-convert-temperature) to convert an absolute
temperature from one scale to another.  With that command, you'll get
the expected 50 degF.

Best regards,
Mauro.

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bug#35608: 26.2; Calc temperature conversions

[npostavs]

close 35608
quit

"Harris, Bill" <wsharris@snopud.com> writes:

> Thank you, Mauro.  I thought it gave absolute temperatures in previous
> versions (26.1, for example), but I just checked on version 25.1, and
> it, too, does as you say.

Right, see also (info "(calc) Basic Operations on Units") or
<https://www.gnu.org/software/emacs/manual/html_node/calc/Basic-Operations-on-Units.html>,
which has exactly this example conversion:

       The ‘u c’ command treats temperature units (like ‘degC’ and ‘K’) as
    relative temperatures.  For example, ‘u c’ converts ‘10 degC’ to ‘18
    degF’: A change of 10 degrees Celsius corresponds to a change of 18
    degrees Fahrenheit.  To convert absolute temperatures, you can use the
    ‘u t’ (‘calc-convert-temperature’) command.  The value on the stack must
    be a simple units expression with units of temperature only.  This
    command would convert ‘10 degC’ to ‘50 degF’, the equivalent temperature
    on the Fahrenheit scale.

bug#35608: 26.2; Calc temperature conversions

[Harris, Bill]

RTM, as they say.  Thanks!

-----Original Message-----
From: npostavs@gmail.com <npostavs@gmail.com> 
Sent: Monday, May 13, 2019 7:50 AM
To: Harris, Bill <wsharris@snopud.com>
Cc: Mauro Aranda <maurooaranda@gmail.com>; 35608@debbugs.gnu.org
Subject: Re: bug#35608: 26.2; Calc temperature conversions

CAUTION: THIS EMAIL IS FROM AN EXTERNAL SENDER.
Do not click on links or open attachments if the sender is unknown or the email is suspect.
________________________________

close 35608
quit

"Harris, Bill" <wsharris@snopud.com> writes:

> Thank you, Mauro.  I thought it gave absolute temperatures in previous 
> versions (26.1, for example), but I just checked on version 25.1, and 
> it, too, does as you say.

Right, see also (info "(calc) Basic Operations on Units") or <https://www.gnu.org/software/emacs/manual/html_node/calc/Basic-Operations-on-Units.html>,
which has exactly this example conversion:

       The 'u c' command treats temperature units (like 'degC' and 'K') as
    relative temperatures.  For example, 'u c' converts '10 degC' to '18
    degF': A change of 10 degrees Celsius corresponds to a change of 18
    degrees Fahrenheit.  To convert absolute temperatures, you can use the
    'u t' ('calc-convert-temperature') command.  The value on the stack must
    be a simple units expression with units of temperature only.  This
    command would convert '10 degC' to '50 degF', the equivalent temperature
    on the Fahrenheit scale.