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I am fairly new in Mathematica and I am trying to work with scalars and vectors. I decided to denote vectors using OverVector (as example, OverVector[F]stands for the force). Any scalar is denoted by a symbol.

When an expression has a multiplication between scalar and vector, the expected outcome should be nullVector, but Mathematica evaluated this as zero. (I have been using Notation package and

Notation[OverVector[0]\[DoubleLongLeftRightArrow] nullVector]

nullVector stands for the zero vector)

How I can prevent Mathematica to evaluate Times[OverVector[F],0] as zero?

In other words. I need Mathematica evaluates the multiplication between vector and zero as the zero vector (nullVector) not as zero. How I can get this?

Thank you so much.

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2 Answers 2

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Using TagSetDelayed allows this definition to be associated with OverVector instead of Times:

OverVector /: Times[OverVector[_], 0] := nullVector
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  • $\begingroup$ Many thanks @Marius. This works perfectly. $\endgroup$ Jan 4, 2016 at 2:13
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One way is

Unprotect[Times];
Times[OverVector[_],0] = nullVector
Protect[Times];

though generally it's not a good idea to redefine built-in commands.

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    $\begingroup$ Thanks @Andrew, I think too it's not a good practice to redefine built-in commands. I´m cheking the code with the @Marius´s idea. $\endgroup$ Jan 4, 2016 at 2:18

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