Symbolic computation ERROR?

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Yuechuan Chen
Yuechuan Chen il 11 Dic 2019
Commentato: Walter Roberson il 12 Dic 2019
p=sym('5744092954902128823202697');
randi([2,p-2])
So I've defined p and tried to compute randi([2,p-2]), Matlab returns: 'Size and range inputs must be numeric.'.
I know it's something to do with the symbolic variable but I do not know why this is happening, nor the solution. Is there a way to do this without converting p to numeric because I don't want to lose precision
THANK YOU!

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Walter Roberson
Walter Roberson il 11 Dic 2019
Modificato: Walter Roberson il 11 Dic 2019
Rsymproc = feval(symengine, 'random', p-3);
Rsym = @() feval(symengine, Rsymproc) + 1;
Now each call to Rsym() will return one random number in the range [2, p-2]
Note: the internal procedure generated for this does not accept array sizes, so to generate multiple values, call Rsym multiple times.
  3 Commenti
Yuechuan Chen
Yuechuan Chen il 12 Dic 2019
Modificato: Yuechuan Chen il 12 Dic 2019
So my interpretation is that Rsymproc generates a random integer in the range [0,p-4], and Rym increases the minima&maxima by 2 so it becomes [2,p-2], and feval just outputs the number generated.
I tried this with p=7 and q=3 and it seemed correct.
Walter Roberson
Walter Roberson il 12 Dic 2019
You do not need to
feval(symengine, Rsym)
You can just
Rsym()
You are correct in your intepretation of how the functions work.

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