Jacobi symbol: Difference between revisions
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=={{header|Factor}}== |
=={{header|Factor}}== |
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The <code>jacobi</code> word already exists in the <code>math.extras</code> vocabulary. See the implementation [https://docs.factorcode.org/content/word-jacobi%2Cmath.extras.html here]. |
The <code>jacobi</code> word already exists in the <code>math.extras</code> vocabulary. See the implementation [https://docs.factorcode.org/content/word-jacobi%2Cmath.extras.html here]. |
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=={{header|Erlang}}== |
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jacobi(_, N) when N < 0 -> 0; |
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jacobi(_, N) when (N band 1) =:= 0 -> 0; % N is even |
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jacobi(A, N) when A < 0 -> |
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J2 = ja(-A, N), |
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case N band 3 of |
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1 -> J2; |
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3 -> -J2 |
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end; |
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jacobi(A, N) -> ja(A, N). |
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ja(0, _) -> 0; |
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ja(1, _) -> 1; |
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ja(A, N) when A >= N -> ja(A rem N, N); |
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ja(A, N) when (A band 1) =:= 0 -> % A is even |
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J2 = ja(A bsr 1, N), |
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case N band 7 of |
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1 -> J2; |
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3 -> -J2; |
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5 -> -J2; |
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7 -> J2 |
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end; |
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ja(A, N) -> % if we get here, A is odd, so we can flip it. |
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J2 = ja(N, A), |
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case (A band 3 =:= 3) and (N band 3 =:= 3) of |
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true -> -J2; |
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false -> J2 |
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end. |
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</lang> |
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=={{header|Go}}== |
=={{header|Go}}== |
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17 0 1 1 -1 1 -1 -1 -1 1 1 |
17 0 1 1 -1 1 -1 -1 -1 1 1 |
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</pre> |
</pre> |
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=={{header|Haskell}}== |
=={{header|Haskell}}== |
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