[PPL-devel] something not clear...

[P M Hill]

On Wed, 1 Nov 2006, Alessandro Vincenzi wrote:

> Hi,
>
> i've started to read the ppl documentation, and i've found a doubt
> reading section at page 8:
>
> 1.4.5 Removing Dimensions from the vector space.
>
> and in particular, how the remove_space_dimension works.
>
> In fact from the example i can not understand why applying the operator
> on the singleton set {(3,1,0,2)^T} in R^4 with the variable set {x_1,
> x_2} we obtain just {(3,2)^T}. Namely, i can not understand which is the
> connection between the set of variables gived to the operator and the
> two dimensions removed from P (i.e the second and the third).

The variables x_1 and x_2 are the second and third dimensions. After 
removing these dimensions, the remaining dimensions (the 1st and 4th) are 
renumbered to be the 1st and 2nd.

If it is not clear, can you suggest a better explanation?

Pat

>
> Instead, the remove_higher_space_dimension operator is simpler because
> is easy to understand that it removes all the dimensions  i >= m.
>
> Thanks,
>
> Alessandro Vincenzi
>
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