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CyclotomicIndex --
computes the index of a given cyclotomic polynomial
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CyclotomicIndex(F: RINGELEM): INT |
This function takes the given polynomial
F and returns
the index
n if it is the
n-th cyclotomic polynomial.
Otherwise, it returns
0. To test whether a polynomial is
cyclotomic, call
CyclotomicIndex and check that the result is non-zero.
There is also
CyclotomicIndex_unchecked. It is correct if
the given polynomial is cyclotomic, but may (rarely) return a non-zero
value if the input polynomial is not cyclotomic. It is faster than
the main function.
/**/ use R ::= QQ[x];
/**/ CyclotomicIndex(x^6 +x^3 +1);
9
/**/ CyclotomicIndex(x^4 -x^2 +2);
0
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