Integer check with a symbolic variable
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Yuechuan Chen
le 12 Déc 2019
Commenté : Yuechuan Chen
le 13 Déc 2019
So I have:
s=sym('10517669');
p=nextprime(8*(S^4));
if float((p-1)/2)==(p-1)/2
...
end
I know float only works for single&double-precision, but p is so large I have to use the symbolic toolbox because it don't want to lose precision.
How could I resolve this?
THANKS
2 commentaires
Fangjun Jiang
le 12 Déc 2019
p is accurately represented using sym object in your code. You know p is an integer from theory. What do you try to do? double(p) or single(p) can't represent p without precision loss.
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Fangjun Jiang
le 13 Déc 2019
If you want to check whether (p-1)/2 is an integer, then check whether p is an odd number. But since p is a prime number, it seems p is always odd except that p==2.
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