23.0.50; calc: units conversion changes value

23.0.50; calc: units conversion changes value

[Torsten Bronger]

Hallöchen!

In Emacs Calc, when I try to convert between incompatible units,
Calc refuses to convert, which is totally correct behaviour.
However, in some cases it changes the value of the quantity, which
isn't in my opinion:

Current value on stack: "1".  Then "calc-convert-units", Old units:
1, new units: cm^2.  The new value on the stack is "100" but I
expect "1".  This is problematic when you mis-typed the new unit and
try it again with the correct one.  Then you get indeed the correct
target unit but (if metric prefixes and at least ^2 is involved)
with the wrong value.

Tschö,
Torsten.

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Re: 23.0.50; calc: units conversion changes value

[Leo]

On 2007-10-23 19:29 +0100, Torsten Bronger wrote:
> Hallöchen!
>
> In Emacs Calc, when I try to convert between incompatible units,
> Calc refuses to convert, which is totally correct behaviour.
> However, in some cases it changes the value of the quantity, which
> isn't in my opinion:
>
> Current value on stack: "1".  Then "calc-convert-units", Old units:
> 1, new units: cm^2.  The new value on the stack is "100" but I
> expect "1". 

I can reproduce this on Emacs 2007-10-10.

> This is problematic when you mis-typed the new unit and try it again
> with the correct one.  Then you get indeed the correct target unit but
> (if metric prefixes and at least ^2 is involved) with the wrong value.
>
> Tschö,
> Torsten.

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Re: 23.0.50; calc: units conversion changes value

[Jay Belanger]

Torsten Bronger <bronger@physik.rwth-aachen.de> writes:

> In Emacs Calc, when I try to convert between incompatible units,
> Calc refuses to convert, which is totally correct behaviour.

Calc will convert to incompatible units, sort of; if the target units
are incompatible, it will multiply them by the appropriate fundamental
units to make the augmented target units compatible.

> However, in some cases it changes the value of the quantity, which
> isn't in my opinion:
>
> Current value on stack: "1".  Then "calc-convert-units", Old units:
> 1, new units: cm^2.  The new value on the stack is "100" but I
> expect "1". 

Thanks for catching this; it's been fixed in CVS.

Jay