Unit precedence

[StuartBruff]

enter 3m*9kg, realize it's an error and should read
'per kilogram'. edit * and replace with /

desired result (3m)/(9kg)
actual result 3(m/9)kg

The question is should Mathcad attempt to group
number/unit combinations into quantities and give
them higher precedence so that the 'desired' result
obtains?

(assume that Mathcad can recognize a unit by either
look up or label)

Stuart

[IRstuff]

On 8/24/2009 3:27:59 AM, stuartafbruff wrote:
>enter 3m*9kg, realize it's an
>error and should read
>'per kilogram'. edit * and
>replace with /
>
>desired result (3m)/(9kg)
>actual result 3(m/9)kg
>
>The question is should Mathcad
>attempt to group
>number/unit combinations into
>quantities and give
>them higher precedence so that
>the 'desired' result
>obtains?
>
>(assume that Mathcad can
>recognize a unit by either
>look up or label)
>
>Stuart

In M11, it was certainly more straightforward. Deleting the operator left a placeholder. Nonetheless, your specific example is just as annoying in M11, since replacing the placeholder with the desired "/" gives you:
3m/9 *kg.

However, since this is a known issue with M11, the workaround remains the same, which is to cut everything that's supposed to go in the denominator first, then delete the multiplication sign.

TTFN,
Eden

[StuartBruff]

On 8/24/2009 10:46:57 AM, eden_mei wrote:
== However, since this is a known issue with M11, the workaround remains the same, which is to cut everything that's supposed to go in the denominator first, then delete the multiplication sign.

Yes, but it's *another* workaround - If they're going to call it Prime, I'd rather it didn't carry over the workarounds from the Dotage of an older (more capable) product. The idea (or so I thought) is to make Prime more intuitive and this is one of those areas where it might make a nice selling point, ie intuitive handling of Quantities.

Stuart

[RichardJ]

On 8/24/2009 10:46:57 AM, eden_mei wrote:

>In M11, it was certainly more
>straightforward. Deleting the operator
>left a placeholder. Nonetheless, your
>specific example is just as annoying in
>M11, since replacing the placeholder
>with the desired "/" gives you:
>3m/9 *kg.

But in Mathcad 11 (or 14) you can select the 9*kg, then backspace to remove the *, then type /, and you get what you want. I can't figure out any way to do it in Prime, and that is a problem. Overall I like the new editor, but it does have some annoying quirks (and this is about the most annoying I've seen).

Richard

[IRstuff]

So, far, my personal scorecard still favors the old editor, just because the freedom of having a variety of approachs to doing something is more appealing than a single, cumbersome, rigid method.

TTFN,
Eden

[SteenGroðe]

Must be a bug (haven't reported it)
When you highlight 9kg from the back to the from and then press delete forward it has to be the multiplication that is deleted. To delete 9kg you must press delete.

Steen Gro�e

[jkucan]

To change 3m*9kg to 3m/9kg, select * (this is new to Mathcad Prime) and enter "/". Notice that when you select *, 3m and 9kg are highlighted indicating what the precedence is.

Hope that helps,
--Jakov Kucan (Mathcad Team)

[RichardJ]

On 8/25/2009 3:13:06 AM, jkucan wrote:
>To change 3m*9kg to 3m/9kg,
>select * (this is new to
>Mathcad Prime) and enter "/".
>Notice that when you select *,
>3m and 9kg are highlighted
>indicating what the precedence
>is.

Hi Jakov

Yes and no. If you enter the expression as 3m*9kg then what you say is true. If you enter it as 3*m*9*kg (the "old Mathcad" way) then the m and 9 are highlighted. So it depends on how you enter the units. If we forget the units, and just make it more general, so the expression is a*b*c*d, then there seems to be no easy way to change the middle * to / so that c*d is on the denominator.

Richard

[TomGutman]

MC' seems to implement multiplication as a polyaddic operator, with repeated multiplication just beign multiple operands. This is different from the formal usage where repeated multiplication is the iterative application of a binary operator. Thus formally a*b*c*d is taken to mean ((a*b)*c)*d. But MC' clearly treats it as *(a,b,c,d) (probably using the lisp form, (*,a,b,c,d). This can be seen as selecting any of the three multiplications highlights just the two adjacent operands.

To convert a*b*c*d to (a*b)/(c*d) you have to first parenthesize the desired groups. Select the first multiplication and parenthesize that (use the "(" key). Then select the last multiplication and parenthesize that. Then select the middle multiplication and replace it with division (enter "/").
__________________
� � � � Tom Gutman

[RichardJ]

On 8/25/2009 4:26:22 PM, Tom_Gutman wrote:

>To convert a*b*c*d to
>(a*b)/(c*d) you have to first
>parenthesize the desired
>groups. Select the first
>multiplication and
>parenthesize that (use the "("
>key). Then select the last
>multiplication and
>parenthesize that. Then
>select the middle
>multiplication and replace it
>with division (enter "/").

And then delete all the unnecessary parentheses. That is an excessively log and painful series of operations to make one simple edit.

This is a really bad feature of the new editor.

Richard

[ValeryOchkov]

On 8/24/2009 3:27:59 AM, stuartafbruff wrote:

>enter 3m*9kg, realize it's an

>error and should read

>'per kilogram'. edit * and

>replace with /

>

>desired result (3m)/(9kg)

>actual result 3(m/9)kg

See too:

Val
http://twt.mpei.ac.ru/ochkov/v_ochkov.htm

[IRstuff]

I reported that one a while ago via email.


TTFN,
Eden