Scalar or vector bug in Mathcad prime 8

Question

Mathcad prime 8 is having trouble understanding Vector quantity. When I open the worksheet, It automatically calculates and throws the error " This value must be scalar or vector".

When the equals sign is deleted and replaced, the worksheet works fine.

But then if I change the units from "m" to "mm", the worksheet looses the vector values again and throws the same error. Can someone confirm if there is permanent solution to this.

P.S: I created this worksheet in Mathcad prime 7.0, recently got prime 8 installed. Could that be reason? Or just this version has the bug.

LucMeekes · Accepted Answer

In Prime 8 you can create a range with units:

It will display as a range (which is not discernable from the display of a vector):

And you can change the unit, from m to mm:

But it stays a range, you cannot index it:

When you define a range and immediately evaluate the definition, you get a vector:

(You can index it:

)

BUT, if you change the result unit, (e.g. from m to mm), you get:

With error: "This value must be a scalar or a matrix", and then of course the variable is undefined:

let alone that you can index it.

To repair, you have to remove the evaluation from the range definition, so remove the =.

After that you can (if you want) re-add the evaluation the arrive (again) at:

It appears that Prime 7 is immune to changing the unit of the evaluation of the definition of a range with units:

Defining a vector through immediate evaluation of a range definition is an undocumented feature/bug. It should not be used, or else with extreme care and realising that this feature/bug can be broken/fixed at any Prime revision.

Success!
Luc

Werner_E · Answer

I can confirm that what you tried works OK in Prime 6.

So obviously they broke something in Prime 8.

But you must be aware that the convenient feature of turning a range into a vector by following the definition immediately by an evaluation always has been an undocumented feature and as such always was a candidate subject to be changed without notice. I guess that for some reason they broke that feature at least when using it with units.

I guess that, even though you cannot change the unit from m to mm in the evaluation after the definition you may be able to do so in a separate region as the conversion from a range into a vector still seems to work (can't test myself as of lack of P8):

The "normal"/"official" ways to create a vector should not been affected, too, I suppose. For instance

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