[Scilab-users] indexing array of rationals

[Federico Miyara]

Stéphane,

You may try, if k is the index,

pi(2)(k)/pi(3)(k)

This is because a rational is a list and the first element is a vector 
of strings describing the structure, not a component of the matrix of 
rationals.

Indeed I think there is not such a thing as a matrix of rationals, but a 
rational (so, itself a list) whose components 2 and 3 are matrices of 
polynomials; respectively, numerator and denominator polynomials.

When one tries to create a matrix of lists (general lists, not 
rationals) it yields an error:

a = list( 1, "a", %s);
b = list( 2, "b", %z);
c = [a,b]

The error message is

Undefined operation for the given operands.
check or define function %l_c_l for overloading.

When the lists are specifically rtationals, the command works fine, for 
instance

d = [(1+%s)/(1+2*%s), (1-%s)/(1+%s+2*%s^2)]

but it is not a matrix of rationals but a rational whose numerator and 
denominator fields are matrices of polynomials

Regards,

Federico Miyara


On 22/07/2021 17:08, Stéphane Mottelet wrote:
> Hi all,
>
> I thought indexing an array of rationals was possible. Likely this is 
> no possible and this is a pity
>
> --> pi
>  pi  =
>
>       θ +2θ²
>     ----------
>     1 +4θ +3θ²
>
>     0.3333333θ
>    ------------
>    0.3333333 +θ
>
>     0.3333333θ
>    ------------
>    0.3333333 +θ
>
>       θ +2θ²
>     ----------
>     1 +4θ +3θ²
>
> --> pi(1)
>  ans  =
>
>   "r"  "num"  "den"  "dt"
>
> Any clue, somebody ?
>


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