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Jacobi symbol

From Rosetta Code
Task
Jacobi symbol
You are encouraged to solve this task according to the task description, using any language you may know.

The Jacobi symbol is a multiplicative function that generalizes the Legendre symbol. Specifically, the Jacobi symbol (a | n) equals the product of the Legendre symbols (a | p_i)^(k_i), where n = p_1^(k_1)*p_2^(k_2)*...*p_i^(k_i) and the Legendre symbol (a | p) denotes the value of a ^ ((p-1)/2) (mod p)

  • (a | p) ≡   1     if a is a square (mod p)
  • (a | p) ≡ -1     if a is not a square (mod p)
  • (a | p) ≡   0     if a ≡ 0

If n is prime, then the Jacobi symbol (a | n) equals the Legendre symbol (a | n).

Task

Calculate the Jacobi symbol (a | n).

Reference

AWK[edit]

Translation of: Go
 
# syntax: GAWK -f JACOBI_SYMBOL.AWK
BEGIN {
max_n = 29
max_a = max_n + 1
printf("n\\a")
for (i=1; i<=max_a; i++) {
printf("%3d",i)
underline = underline " --"
}
printf("\n---%s\n",underline)
for (n=1; n<=max_n; n+=2) {
printf("%3d",n)
for (a=1; a<=max_a; a++) {
printf("%3d",jacobi(a,n))
}
printf("\n")
}
exit(0)
}
function jacobi(a,n, result,tmp) {
if (n%2 == 0) {
print("error: 'n' must be a positive odd integer")
exit
}
a %= n
result = 1
while (a != 0) {
while (a%2 == 0) {
a /= 2
if (n%8 == 3 || n%8 == 5) {
result = -result
}
}
tmp = a
a = n
n = tmp
if (a%4 == 3 && n%4 == 3) {
result = -result
}
a %= n
}
if (n == 1) {
return(result)
}
return(0)
}
 
Output:
n\a  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
--- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1
  3  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0
  5  1 -1 -1  1  0  1 -1 -1  1  0  1 -1 -1  1  0  1 -1 -1  1  0  1 -1 -1  1  0  1 -1 -1  1  0
  7  1  1 -1  1 -1 -1  0  1  1 -1  1 -1 -1  0  1  1 -1  1 -1 -1  0  1  1 -1  1 -1 -1  0  1  1
  9  1  1  0  1  1  0  1  1  0  1  1  0  1  1  0  1  1  0  1  1  0  1  1  0  1  1  0  1  1  0
 11  1 -1  1  1  1 -1 -1 -1  1 -1  0  1 -1  1  1  1 -1 -1 -1  1 -1  0  1 -1  1  1  1 -1 -1 -1
 13  1 -1  1  1 -1 -1 -1 -1  1  1 -1  1  0  1 -1  1  1 -1 -1 -1 -1  1  1 -1  1  0  1 -1  1  1
 15  1  1  0  1  0  0 -1  1  0  0 -1  0 -1 -1  0  1  1  0  1  0  0 -1  1  0  0 -1  0 -1 -1  0
 17  1  1 -1  1 -1 -1 -1  1  1 -1 -1 -1  1 -1  1  1  0  1  1 -1  1 -1 -1 -1  1  1 -1 -1 -1  1
 19  1 -1 -1  1  1  1  1 -1  1 -1  1 -1 -1 -1 -1  1  1 -1  0  1 -1 -1  1  1  1  1 -1  1 -1  1
 21  1 -1  0  1  1  0  0 -1  0 -1 -1  0 -1  0  0  1  1  0 -1  1  0  1 -1  0  1  1  0  0 -1  0
 23  1  1  1  1 -1  1 -1  1  1 -1 -1  1  1 -1 -1  1 -1  1 -1 -1 -1 -1  0  1  1  1  1 -1  1 -1
 25  1  1  1  1  0  1  1  1  1  0  1  1  1  1  0  1  1  1  1  0  1  1  1  1  0  1  1  1  1  0
 27  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0
 29  1 -1 -1  1  1  1  1 -1  1 -1 -1 -1  1 -1 -1  1 -1 -1 -1  1 -1  1  1  1  1 -1 -1  1  0  1


C[edit]

#include <stdlib.h>
#include <stdio.h>
 
#define SWAP(a, b) (((a) ^= (b)), ((b) ^= (a)), ((a) ^= (b)))
 
int jacobi(unsigned long a, unsigned long n) {
if (a >= n) a %= n;
int result = 1;
while (a) {
while ((a & 1) == 0) {
a >>= 1;
if ((n & 7) == 3 || (n & 7) == 5) result = -result;
}
SWAP(a, n);
if ((a & 3) == 3 && (n & 3) == 3) result = -result;
a %= n;
}
if (n == 1) return result;
return 0;
}
 
void print_table(unsigned kmax, unsigned nmax) {
printf("n\\k|");
for (int k = 0; k <= kmax; ++k) printf("%'3u", k);
printf("\n----");
for (int k = 0; k <= kmax; ++k) printf("---");
putchar('\n');
for (int n = 1; n <= nmax; n += 2) {
printf("%-2u |", n);
for (int k = 0; k <= kmax; ++k)
printf("%'3d", jacobi(k, n));
putchar('\n');
}
}
 
int main() {
print_table(20, 21);
return 0;
}
Output:
n\k|  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20
---+---------------------------------------------------------------
1  |  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1
3  |  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1
5  |  0  1 -1 -1  1  0  1 -1 -1  1  0  1 -1 -1  1  0  1 -1 -1  1  0
7  |  0  1  1 -1  1 -1 -1  0  1  1 -1  1 -1 -1  0  1  1 -1  1 -1 -1
9  |  0  1  1  0  1  1  0  1  1  0  1  1  0  1  1  0  1  1  0  1  1
11 |  0  1 -1  1  1  1 -1 -1 -1  1 -1  0  1 -1  1  1  1 -1 -1 -1  1
13 |  0  1 -1  1  1 -1 -1 -1 -1  1  1 -1  1  0  1 -1  1  1 -1 -1 -1
15 |  0  1  1  0  1  0  0 -1  1  0  0 -1  0 -1 -1  0  1  1  0  1  0
17 |  0  1  1 -1  1 -1 -1 -1  1  1 -1 -1 -1  1 -1  1  1  0  1  1 -1
19 |  0  1 -1 -1  1  1  1  1 -1  1 -1  1 -1 -1 -1 -1  1  1 -1  0  1
21 |  0  1 -1  0  1  1  0  0 -1  0 -1 -1  0 -1  0  0  1  1  0 -1  1


C++[edit]

#include <algorithm>
#include <cassert>
#include <iomanip>
#include <iostream>
 
int jacobi(int n, int k) {
assert(k > 0 && k % 2 == 1);
n %= k;
int t = 1;
while (n != 0) {
while (n % 2 == 0) {
n /= 2;
int r = k % 8;
if (r == 3 || r == 5)
t = -t;
}
std::swap(n, k);
if (n % 4 == 3 && k % 4 == 3)
t = -t;
n %= k;
}
return k == 1 ? t : 0;
}
 
void print_table(std::ostream& out, int kmax, int nmax) {
out << "n\\k|";
for (int k = 0; k <= kmax; ++k)
out << ' ' << std::setw(2) << k;
out << "\n----";
for (int k = 0; k <= kmax; ++k)
out << "---";
out << '\n';
for (int n = 1; n <= nmax; n += 2) {
out << std::setw(2) << n << " |";
for (int k = 0; k <= kmax; ++k)
out << ' ' << std::setw(2) << jacobi(k, n);
out << '\n';
}
}
 
int main() {
print_table(std::cout, 20, 21);
return 0;
}
Output:
n\k|  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20
-------------------------------------------------------------------
 1 |  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1
 3 |  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1
 5 |  0  1 -1 -1  1  0  1 -1 -1  1  0  1 -1 -1  1  0  1 -1 -1  1  0
 7 |  0  1  1 -1  1 -1 -1  0  1  1 -1  1 -1 -1  0  1  1 -1  1 -1 -1
 9 |  0  1  1  0  1  1  0  1  1  0  1  1  0  1  1  0  1  1  0  1  1
11 |  0  1 -1  1  1  1 -1 -1 -1  1 -1  0  1 -1  1  1  1 -1 -1 -1  1
13 |  0  1 -1  1  1 -1 -1 -1 -1  1  1 -1  1  0  1 -1  1  1 -1 -1 -1
15 |  0  1  1  0  1  0  0 -1  1  0  0 -1  0 -1 -1  0  1  1  0  1  0
17 |  0  1  1 -1  1 -1 -1 -1  1  1 -1 -1 -1  1 -1  1  1  0  1  1 -1
19 |  0  1 -1 -1  1  1  1  1 -1  1 -1  1 -1 -1 -1 -1  1  1 -1  0  1
21 |  0  1 -1  0  1  1  0  0 -1  0 -1 -1  0 -1  0  0  1  1  0 -1  1

Crystal[edit]

Translation of: Swift
def jacobi(a, n)
raise ArgumentError.new "n must b positive and odd" if n < 1 || n.even?
res = 1
until (a %= n) == 0
while a.even?
a >>= 1
res = -res if [3, 5].includes? n % 8
end
a, n = n, a
res = -res if a % 4 == n % 4 == 3
end
n == 1 ? res : 0
end
 
puts "Jacobian symbols for jacobi(a, n)"
puts "n\\a 0 1 2 3 4 5 6 7 8 9 10"
puts "------------------------------------"
1.step(to: 17, by: 2) do |n|
printf("%2d ", n)
(0..10).each { |a| printf(" % 2d", jacobi(a, n)) }
puts
end
Output:
Jacobian symbols for jacobi(a, n)
n\a  0  1  2  3  4  5  6  7  8  9 10
------------------------------------
 1   1  1  1  1  1  1  1  1  1  1  1
 3   0  1 -1  0  1 -1  0  1 -1  0  1
 5   0  1 -1 -1  1  0  1 -1 -1  1  0
 7   0  1  1 -1  1 -1 -1  0  1  1 -1
 9   0  1  1  0  1  1  0  1  1  0  1
11   0  1 -1  1  1  1 -1 -1 -1  1 -1
13   0  1 -1  1  1 -1 -1 -1 -1  1  1
15   0  1  1  0  1  0  0 -1  1  0  0
17   0  1  1 -1  1 -1 -1 -1  1  1 -1

Erlang[edit]

 
jacobi(_, N) when N =< 0 -> jacobi_domain_error;
jacobi(_, N) when (N band 1) =:= 0 -> jacobi_domain_error;
jacobi(A, N) when A < 0 ->
J2 = ja(-A, N),
case N band 3 of
1 -> J2;
3 -> -J2
end;
jacobi(A, N) -> ja(A, N).
 
ja(0, _) -> 0;
ja(1, _) -> 1;
ja(A, N) when A >= N -> ja(A rem N, N);
ja(A, N) when (A band 1) =:= 0 -> % A is even
J2 = ja(A bsr 1, N),
case N band 7 of
1 -> J2;
3 -> -J2;
5 -> -J2;
7 -> J2
end;
ja(A, N) -> % if we get here, A is odd, so we can flip it.
J2 = ja(N, A),
case (A band 3 =:= 3) and (N band 3 =:= 3) of
true -> -J2;
false -> J2
end.
 

F#[edit]

 
//Jacobi Symbol. Nigel Galloway: July 14th., 2020
let J n m=let rec J n m g=match n with
0->if m=1 then g else 0
|n when n%2=0->J(n/2) m (if m%8=3 || m%8=5 then -g else g)
|n->J (m%n) n (if m%4=3 && n%4=3 then -g else g)
J (n%m) m 1
printfn "n\m 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30\n ----------------------------------------------------------------------------------------------------------------------"
[1..2..29]|>List.iter(fun m->printf "%3d" m; [1..30]|>List.iter(fun n->printf "%4d" (J n m)); printfn "")
 
Output:
n\m   1   2   3   4   5   6   7   8   9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30
     ----------------------------------------------------------------------------------------------------------------------
  1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1
  3   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0
  5   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0
  7   1   1  -1   1  -1  -1   0   1   1  -1   1  -1  -1   0   1   1  -1   1  -1  -1   0   1   1  -1   1  -1  -1   0   1   1
  9   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0
 11   1  -1   1   1   1  -1  -1  -1   1  -1   0   1  -1   1   1   1  -1  -1  -1   1  -1   0   1  -1   1   1   1  -1  -1  -1
 13   1  -1   1   1  -1  -1  -1  -1   1   1  -1   1   0   1  -1   1   1  -1  -1  -1  -1   1   1  -1   1   0   1  -1   1   1
 15   1   1   0   1   0   0  -1   1   0   0  -1   0  -1  -1   0   1   1   0   1   0   0  -1   1   0   0  -1   0  -1  -1   0
 17   1   1  -1   1  -1  -1  -1   1   1  -1  -1  -1   1  -1   1   1   0   1   1  -1   1  -1  -1  -1   1   1  -1  -1  -1   1
 19   1  -1  -1   1   1   1   1  -1   1  -1   1  -1  -1  -1  -1   1   1  -1   0   1  -1  -1   1   1   1   1  -1   1  -1   1
 21   1  -1   0   1   1   0   0  -1   0  -1  -1   0  -1   0   0   1   1   0  -1   1   0   1  -1   0   1   1   0   0  -1   0
 23   1   1   1   1  -1   1  -1   1   1  -1  -1   1   1  -1  -1   1  -1   1  -1  -1  -1  -1   0   1   1   1   1  -1   1  -1
 25   1   1   1   1   0   1   1   1   1   0   1   1   1   1   0   1   1   1   1   0   1   1   1   1   0   1   1   1   1   0
 27   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0
 29   1  -1  -1   1   1   1   1  -1   1  -1  -1  -1   1  -1  -1   1  -1  -1  -1   1  -1   1   1   1   1  -1  -1   1   0   1

Factor[edit]

The jacobi word already exists in the math.extras vocabulary. See the implementation here.

FreeBASIC[edit]

function gcdp( a as uinteger, b as uinteger ) as uinteger
if b = 0 then return a
return gcdp( b, a mod b )
end function
 
function gcd(a as integer, b as integer) as uinteger
return gcdp( abs(a), abs(b) )
end function
 
function jacobi( a as uinteger, n as uinteger ) as integer
if gcd(a, n)<>1 then return 0
if a = 1 then return 1
if a>n then return jacobi( a mod n, n )
if a mod 2 = 0 then
if n mod 8 = 1 or n mod 8 = 7 then
return jacobi(a/2, n)
else
return -jacobi(a/2, n)
end if
end if
dim as integer q = (-1)^((a-1)/2 * (n-1)/2)
return q/jacobi(n, a)
end function
 
'print a table
 
function padto( i as ubyte, j as integer ) as string
return wspace(i-len(str(j)))+str(j)
end function
 
dim as uinteger pn, k, prime(0 to 16) = {3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61}
dim as string outstr = " k "
 
for k = 1 to 36
outstr = outstr + padto(2, k)+" "
next k
print outstr
print " n"
for pn=0 to 16
outstr= " "+padto( 2, prime(pn) )+" "
for k = 1 to 36
outstr = outstr + padto(2, jacobi(k, prime(pn))) + " "
next k
print outstr
next pn
Output:
  k        1   2   3   4   5   6   7   8   9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  
 n
  3        1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0  
  5        1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0   1  
  7        1   1  -1   1  -1  -1   0   1   1  -1   1  -1  -1   0   1   1  -1   1  -1  -1   0   1   1  -1   1  -1  -1   0   1   1  -1   1  -1  -1   0   1  
 11        1  -1   1   1   1  -1  -1  -1   1  -1   0   1  -1   1   1   1  -1  -1  -1   1  -1   0   1  -1   1   1   1  -1  -1  -1   1  -1   0   1  -1   1  
 13        1  -1   1   1  -1  -1  -1  -1   1   1  -1   1   0   1  -1   1   1  -1  -1  -1  -1   1   1  -1   1   0   1  -1   1   1  -1  -1  -1  -1   1   1  
 17        1   1  -1   1  -1  -1  -1   1   1  -1  -1  -1   1  -1   1   1   0   1   1  -1   1  -1  -1  -1   1   1  -1  -1  -1   1  -1   1   1   0   1   1  
 19        1  -1  -1   1   1   1   1  -1   1  -1   1  -1  -1  -1  -1   1   1  -1   0   1  -1  -1   1   1   1   1  -1   1  -1   1  -1  -1  -1  -1   1   1  
 23        1   1   1   1  -1   1  -1   1   1  -1  -1   1   1  -1  -1   1  -1   1  -1  -1  -1  -1   0   1   1   1   1  -1   1  -1   1   1  -1  -1   1   1  
 29        1  -1  -1   1   1   1   1  -1   1  -1  -1  -1   1  -1  -1   1  -1  -1  -1   1  -1   1   1   1   1  -1  -1   1   0   1  -1  -1   1   1   1   1  
 31        1   1  -1   1   1  -1   1   1   1   1  -1  -1  -1   1  -1   1  -1   1   1   1  -1  -1  -1  -1   1  -1  -1   1  -1  -1   0   1   1  -1   1   1  
 37        1  -1   1   1  -1  -1   1  -1   1   1   1   1  -1  -1  -1   1  -1  -1  -1  -1   1  -1  -1  -1   1   1   1   1  -1   1  -1  -1   1   1  -1   1  
 41        1   1  -1   1   1  -1  -1   1   1   1  -1  -1  -1  -1  -1   1  -1   1  -1   1   1  -1   1  -1   1  -1  -1  -1  -1  -1   1   1   1  -1  -1   1  
 43        1  -1  -1   1  -1   1  -1  -1   1   1   1  -1   1   1   1   1   1  -1  -1  -1   1  -1   1   1   1  -1  -1  -1  -1  -1   1  -1  -1  -1   1   1  
 47        1   1   1   1  -1   1   1   1   1  -1  -1   1  -1   1  -1   1   1   1  -1  -1   1  -1  -1   1   1  -1   1   1  -1  -1  -1   1  -1   1  -1   1  
 53        1  -1  -1   1  -1   1   1  -1   1   1   1  -1   1  -1   1   1   1  -1  -1  -1  -1  -1  -1   1   1  -1  -1   1   1  -1  -1  -1  -1  -1  -1   1  
 59        1  -1   1   1   1  -1   1  -1   1  -1  -1   1  -1  -1   1   1   1  -1   1   1   1   1  -1  -1   1   1   1   1   1  -1  -1  -1  -1  -1   1   1  
 61        1  -1   1   1   1  -1  -1  -1   1  -1  -1   1   1   1   1   1  -1  -1   1   1  -1   1  -1  -1   1  -1   1  -1  -1  -1  -1  -1  -1   1  -1   1

Go[edit]

The big.Jacobi function in the standard library (for 'big integers') returns the Jacobi symbol for given values of 'a' and 'n'.

This translates the Lua code in the above referenced Wikipedia article to Go (for 8 byte integers) and checks that it gives the same answers for a small table of values - which it does.

package main
 
import (
"fmt"
"log"
"math/big"
)
 
func jacobi(a, n uint64) int {
if n%2 == 0 {
log.Fatal("'n' must be a positive odd integer")
}
a %= n
result := 1
for a != 0 {
for a%2 == 0 {
a /= 2
nn := n % 8
if nn == 3 || nn == 5 {
result = -result
}
}
a, n = n, a
if a%4 == 3 && n%4 == 3 {
result = -result
}
a %= n
}
if n == 1 {
return result
}
return 0
}
 
func main() {
fmt.Println("Using hand-coded version:")
fmt.Println("n/a 0 1 2 3 4 5 6 7 8 9")
fmt.Println("---------------------------------")
for n := uint64(1); n <= 17; n += 2 {
fmt.Printf("%2d ", n)
for a := uint64(0); a <= 9; a++ {
fmt.Printf(" % d", jacobi(a, n))
}
fmt.Println()
}
 
ba, bn := new(big.Int), new(big.Int)
fmt.Println("\nUsing standard library function:")
fmt.Println("n/a 0 1 2 3 4 5 6 7 8 9")
fmt.Println("---------------------------------")
for n := uint64(1); n <= 17; n += 2 {
fmt.Printf("%2d ", n)
for a := uint64(0); a <= 9; a++ {
ba.SetUint64(a)
bn.SetUint64(n)
fmt.Printf(" % d", big.Jacobi(ba, bn))
}
fmt.Println()
}
}
Output:
Using hand-coded version:
n/a  0  1  2  3  4  5  6  7  8  9
---------------------------------
 1   1  1  1  1  1  1  1  1  1  1
 3   0  1 -1  0  1 -1  0  1 -1  0
 5   0  1 -1 -1  1  0  1 -1 -1  1
 7   0  1  1 -1  1 -1 -1  0  1  1
 9   0  1  1  0  1  1  0  1  1  0
11   0  1 -1  1  1  1 -1 -1 -1  1
13   0  1 -1  1  1 -1 -1 -1 -1  1
15   0  1  1  0  1  0  0 -1  1  0
17   0  1  1 -1  1 -1 -1 -1  1  1

Using standard library function:
n/a  0  1  2  3  4  5  6  7  8  9
---------------------------------
 1   1  1  1  1  1  1  1  1  1  1
 3   0  1 -1  0  1 -1  0  1 -1  0
 5   0  1 -1 -1  1  0  1 -1 -1  1
 7   0  1  1 -1  1 -1 -1  0  1  1
 9   0  1  1  0  1  1  0  1  1  0
11   0  1 -1  1  1  1 -1 -1 -1  1
13   0  1 -1  1  1 -1 -1 -1 -1  1
15   0  1  1  0  1  0  0 -1  1  0
17   0  1  1 -1  1 -1 -1 -1  1  1

Haskell[edit]

Translation of: Scheme
jacobi :: Integer -> Integer -> Integer
jacobi 0 1 = 1
jacobi 0 _ = 0
jacobi a n =
let a_mod_n = rem a n
in if even a_mod_n
then case rem n 8 of
1 -> jacobi (div a_mod_n 2) n
3 -> negate $ jacobi (div a_mod_n 2) n
5 -> negate $ jacobi (div a_mod_n 2) n
7 -> jacobi (div a_mod_n 2) n
else if rem a_mod_n 4 == 3 && rem n 4 == 3
then negate $ jacobi n a_mod_n
else jacobi n a_mod_n


Or, expressing it slightly differently, and adding a tabulation:

import Data.List (replicate, transpose)
import Data.List.Split (chunksOf)
import Data.Bool (bool)
 
jacobi :: Int -> Int -> Int
jacobi = go
where
go 0 1 = 1
go 0 _ = 0
go x y
| even r = plusMinus (rem y 8 `elem` [3, 5]) (go (div r 2) y)
| otherwise = plusMinus (p r && p y) (go y r)
where
plusMinus = bool id negate
p = (3 ==) . flip rem 4
r = rem x y
 
------------------------- DISPLAY -------------------------
jacobiTable :: Int -> Int -> String
jacobiTable nCols nRows =
let rowLabels = [1,3 .. (2 * nRows)]
colLabels = [0 .. pred nCols]
in withColumnLabels ("" : fmap show colLabels) $
labelledRows (fmap show rowLabels) $
paddedCols $
chunksOf nRows $
uncurry jacobi <$> ((,) <$> colLabels <*> rowLabels)
 
-------------------------- TEST ---------------------------
main :: IO ()
main = putStrLn $ jacobiTable 11 9
 
------------------ TABULATION FUNCTIONS -------------------
paddedCols
:: Show a
=> [[a]] -> [[String]]
paddedCols cols =
let scols = fmap show <$> cols
w = maximum $ length <$> concat scols
in map (justifyRight w ' ') <$> scols
 
labelledRows :: [String] -> [[String]] -> [[String]]
labelledRows labels cols =
let w = maximum $ map length labels
in zipWith (:) ((++ " ->") . justifyRight w ' ' <$> labels) (transpose cols)
 
withColumnLabels :: [String] -> [[String]] -> String
withColumnLabels labels rows@(x:_) =
let labelRow = unwords $ zipWith (`justifyRight` ' ') (length <$> x) labels
in unlines $ labelRow : replicate (length labelRow) '-' : fmap unwords rows
 
justifyRight :: Int -> a -> [a] -> [a]
justifyRight n c = (drop . length) <*> (replicate n c ++)
Output:
       0  1  2  3  4  5  6  7  8  9 10
--------------------------------------
 1 ->  1  1  1  1  1  1  1  1  1  1  1
 3 ->  0  1 -1  0  1 -1  0  1 -1  0  1
 5 ->  0  1 -1 -1  1  0  1 -1 -1  1  0
 7 ->  0  1  1 -1  1 -1 -1  0  1  1 -1
 9 ->  0  1  1  0  1  1  0  1  1  0  1
11 ->  0  1 -1  1  1  1 -1 -1 -1  1 -1
13 ->  0  1 -1  1  1 -1 -1 -1 -1  1  1
15 ->  0  1  1  0  1  0  0 -1  1  0  0
17 ->  0  1  1 -1  1 -1 -1 -1  1  1 -1

J[edit]

 
NB. direct translation of the Lua program found
NB. at the wikipedia entry incorporated here in comments.
 
NB.function jacobi(n, k)
jacobi=: dyad define every
 
k=. x NB. k is the left argument
n=. y NB. n is the right hand argument
 
NB.assert(k > 0 and k % 2 == 1)
assert. (k > 0) *. 1 = 2 | k
 
NB.n = n % k
n =. k | n
 
NB.t = 1
t =. 1
 
NB.while n ~= 0 do
while. n do.
 
NB. while n % 2 == 0 do
while. -. 2 | n do.
 
NB. n = n / 2
n =. <. n % 2
 
NB. r = k % 8
r =. 8 | k
 
NB. if r == 3 or r == 5 then
if. r e. 3 5 do.
 
NB. t = -t
t =. -t
 
NB. end
end.
 
NB. end
end.
 
NB. n, k = k, n
'n k' =. k , n
 
NB. if n % 4 == 3 and k % 4 == 3 then
if. (3 = 4 | n) *. (3 = 4 | k) do.
 
NB. t = -t
t =. -t
 
NB. end
end.
 
NB. n = n % k
n =. k | n
 
NB.end
end.
 
NB.if k == 1 then
if. k = 1 do.
 
NB. return t
t
 
NB.else
else.
 
NB. return 0
0
 
NB.end
end.
 
NB.end
)
 
   k=: 1 2 p. i. 30
   n=: #\ k

   k jacobi table n
+------+--------------------------------------------------------------------------------------+
|jacobi|1  2  3 4  5  6  7  8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30|
+------+--------------------------------------------------------------------------------------+
| 1    |1  1  1 1  1  1  1  1 1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1|
| 3    |1 _1  0 1 _1  0  1 _1 0  1 _1  0  1 _1  0  1 _1  0  1 _1  0  1 _1  0  1 _1  0  1 _1  0|
| 5    |1 _1 _1 1  0  1 _1 _1 1  0  1 _1 _1  1  0  1 _1 _1  1  0  1 _1 _1  1  0  1 _1 _1  1  0|
| 7    |1  1 _1 1 _1 _1  0  1 1 _1  1 _1 _1  0  1  1 _1  1 _1 _1  0  1  1 _1  1 _1 _1  0  1  1|
| 9    |1  1  0 1  1  0  1  1 0  1  1  0  1  1  0  1  1  0  1  1  0  1  1  0  1  1  0  1  1  0|
|11    |1 _1  1 1  1 _1 _1 _1 1 _1  0  1 _1  1  1  1 _1 _1 _1  1 _1  0  1 _1  1  1  1 _1 _1 _1|
|13    |1 _1  1 1 _1 _1 _1 _1 1  1 _1  1  0  1 _1  1  1 _1 _1 _1 _1  1  1 _1  1  0  1 _1  1  1|
|15    |1  1  0 1  0  0 _1  1 0  0 _1  0 _1 _1  0  1  1  0  1  0  0 _1  1  0  0 _1  0 _1 _1  0|
|17    |1  1 _1 1 _1 _1 _1  1 1 _1 _1 _1  1 _1  1  1  0  1  1 _1  1 _1 _1 _1  1  1 _1 _1 _1  1|
|19    |1 _1 _1 1  1  1  1 _1 1 _1  1 _1 _1 _1 _1  1  1 _1  0  1 _1 _1  1  1  1  1 _1  1 _1  1|
|21    |1 _1  0 1  1  0  0 _1 0 _1 _1  0 _1  0  0  1  1  0 _1  1  0  1 _1  0  1  1  0  0 _1  0|
|23    |1  1  1 1 _1  1 _1  1 1 _1 _1  1  1 _1 _1  1 _1  1 _1 _1 _1 _1  0  1  1  1  1 _1  1 _1|
|25    |1  1  1 1  0  1  1  1 1  0  1  1  1  1  0  1  1  1  1  0  1  1  1  1  0  1  1  1  1  0|
|27    |1 _1  0 1 _1  0  1 _1 0  1 _1  0  1 _1  0  1 _1  0  1 _1  0  1 _1  0  1 _1  0  1 _1  0|
|29    |1 _1 _1 1  1  1  1 _1 1 _1 _1 _1  1 _1 _1  1 _1 _1 _1  1 _1  1  1  1  1 _1 _1  1  0  1|
|31    |1  1 _1 1  1 _1  1  1 1  1 _1 _1 _1  1 _1  1 _1  1  1  1 _1 _1 _1 _1  1 _1 _1  1 _1 _1|
|33    |1  1  0 1 _1  0 _1  1 0 _1  0  0 _1 _1  0  1  1  0 _1 _1  0  0 _1  0  1 _1  0 _1  1  0|
|35    |1 _1  1 1  0 _1  0 _1 1  0  1  1  1  0  0  1  1 _1 _1  0  0 _1 _1 _1  0 _1  1  0  1  0|
|37    |1 _1  1 1 _1 _1  1 _1 1  1  1  1 _1 _1 _1  1 _1 _1 _1 _1  1 _1 _1 _1  1  1  1  1 _1  1|
|39    |1  1  0 1  1  0 _1  1 0  1  1  0  0 _1  0  1 _1  0 _1  1  0  1 _1  0  1  0  0 _1 _1  0|
|41    |1  1 _1 1  1 _1 _1  1 1  1 _1 _1 _1 _1 _1  1 _1  1 _1  1  1 _1  1 _1  1 _1 _1 _1 _1 _1|
|43    |1 _1 _1 1 _1  1 _1 _1 1  1  1 _1  1  1  1  1  1 _1 _1 _1  1 _1  1  1  1 _1 _1 _1 _1 _1|
|45    |1 _1  0 1  0  0 _1 _1 0  0  1  0 _1  1  0  1 _1  0  1  0  0 _1 _1  0  0  1  0 _1  1  0|
|47    |1  1  1 1 _1  1  1  1 1 _1 _1  1 _1  1 _1  1  1  1 _1 _1  1 _1 _1  1  1 _1  1  1 _1 _1|
|49    |1  1  1 1  1  1  0  1 1  1  1  1  1  0  1  1  1  1  1  1  0  1  1  1  1  1  1  0  1  1|
|51    |1 _1  0 1  1  0 _1 _1 0 _1  1  0  1  1  0  1  0  0  1  1  0 _1  1  0  1 _1  0 _1  1  0|
|53    |1 _1 _1 1 _1  1  1 _1 1  1  1 _1  1 _1  1  1  1 _1 _1 _1 _1 _1 _1  1  1 _1 _1  1  1 _1|
|55    |1  1 _1 1  0 _1  1  1 1  0  0 _1  1  1  0  1  1  1 _1  0 _1  0 _1 _1  0  1 _1  1 _1  0|
|57    |1  1  0 1 _1  0  1  1 0 _1 _1  0 _1  1  0  1 _1  0  0 _1  0 _1 _1  0  1 _1  0  1  1  0|
|59    |1 _1  1 1  1 _1  1 _1 1 _1 _1  1 _1 _1  1  1  1 _1  1  1  1  1 _1 _1  1  1  1  1  1 _1|
+------+--------------------------------------------------------------------------------------+

Java[edit]

 
 
public class JacobiSymbol {
 
public static void main(String[] args) {
int max = 30;
System.out.printf("n\\k ");
for ( int k = 1 ; k <= max ; k++ ) {
System.out.printf("%2d ", k);
}
System.out.printf("%n");
for ( int n = 1 ; n <= max ; n += 2 ) {
System.out.printf("%2d ", n);
for ( int k = 1 ; k <= max ; k++ ) {
System.out.printf("%2d ", jacobiSymbol(k, n));
}
System.out.printf("%n");
}
}
 
 
// Compute (k n), where k is numerator
private static int jacobiSymbol(int k, int n) {
if ( k < 0 || n % 2 == 0 ) {
throw new IllegalArgumentException("Invalid value. k = " + k + ", n = " + n);
}
k %= n;
int jacobi = 1;
while ( k > 0 ) {
while ( k % 2 == 0 ) {
k /= 2;
int r = n % 8;
if ( r == 3 || r == 5 ) {
jacobi = -jacobi;
}
}
int temp = n;
n = k;
k = temp;
if ( k % 4 == 3 && n % 4 == 3 ) {
jacobi = -jacobi;
}
k %= n;
}
if ( n == 1 ) {
return jacobi;
}
return 0;
}
 
}
 
Output:
n\k  1   2   3   4   5   6   7   8   9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  
 1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1  
 3   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0  
 5   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0  
 7   1   1  -1   1  -1  -1   0   1   1  -1   1  -1  -1   0   1   1  -1   1  -1  -1   0   1   1  -1   1  -1  -1   0   1   1  
 9   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0  
11   1  -1   1   1   1  -1  -1  -1   1  -1   0   1  -1   1   1   1  -1  -1  -1   1  -1   0   1  -1   1   1   1  -1  -1  -1  
13   1  -1   1   1  -1  -1  -1  -1   1   1  -1   1   0   1  -1   1   1  -1  -1  -1  -1   1   1  -1   1   0   1  -1   1   1  
15   1   1   0   1   0   0  -1   1   0   0  -1   0  -1  -1   0   1   1   0   1   0   0  -1   1   0   0  -1   0  -1  -1   0  
17   1   1  -1   1  -1  -1  -1   1   1  -1  -1  -1   1  -1   1   1   0   1   1  -1   1  -1  -1  -1   1   1  -1  -1  -1   1  
19   1  -1  -1   1   1   1   1  -1   1  -1   1  -1  -1  -1  -1   1   1  -1   0   1  -1  -1   1   1   1   1  -1   1  -1   1  
21   1  -1   0   1   1   0   0  -1   0  -1  -1   0  -1   0   0   1   1   0  -1   1   0   1  -1   0   1   1   0   0  -1   0  
23   1   1   1   1  -1   1  -1   1   1  -1  -1   1   1  -1  -1   1  -1   1  -1  -1  -1  -1   0   1   1   1   1  -1   1  -1  
25   1   1   1   1   0   1   1   1   1   0   1   1   1   1   0   1   1   1   1   0   1   1   1   1   0   1   1   1   1   0  
27   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0  
29   1  -1  -1   1   1   1   1  -1   1  -1  -1  -1   1  -1  -1   1  -1  -1  -1   1  -1   1   1   1   1  -1  -1   1   0   1  

Julia[edit]

Translation of: Python
function jacobi(a, n)
a %= n
result = 1
while a != 0
while iseven(a)
a ÷= 2
((n % 8) in [3, 5]) && (result *= -1)
end
a, n = n, a
(a % 4 == n % 4 == 3) && (result *= -1)
a %= n
end
return n == 1 ? result : 0
end
 
print(" Table of jacobi(a, n) for a 1 to 12, n 1 to 31\n 1 2 3 4 5 6 7 8",
" 9 10 11 12\nn\n_____________________________________________________")
for n in 1:2:31
print("\n", rpad(n, 3))
for a in 1:11
print(lpad(jacobi(a, n), 4))
end
end
 
Output:
 Table of jacobi(a, n) for a 1 to 12, n 1 to 31
   1   2   3   4   5   6   7   8   9  10  11  12
n
_____________________________________________________
1     1   1   1   1   1   1   1   1   1   1   1
3     1  -1   0   1  -1   0   1  -1   0   1  -1
5     1  -1  -1   1   0   1  -1  -1   1   0   1
7     1   1  -1   1  -1  -1   0   1   1  -1   1
9     1   1   0   1   1   0   1   1   0   1   1
11    1  -1   1   1   1  -1  -1  -1   1  -1   0
13    1  -1   1   1  -1  -1  -1  -1   1   1  -1
15    1   1   0   1   0   0  -1   1   0   0  -1
17    1   1  -1   1  -1  -1  -1   1   1  -1  -1
19    1  -1  -1   1   1   1   1  -1   1  -1   1
21    1  -1   0   1   1   0   0  -1   0  -1  -1
23    1   1   1   1  -1   1  -1   1   1  -1  -1
25    1   1   1   1   0   1   1   1   1   0   1
27    1  -1   0   1  -1   0   1  -1   0   1  -1
29    1  -1  -1   1   1   1   1  -1   1  -1  -1
31    1   1  -1   1   1  -1   1   1   1   1  -1

Kotlin[edit]

fun jacobi(A: Int, N: Int): Int {
assert(N > 0 && N and 1 == 1)
var a = A % N
var n = N
var result = 1
while (a != 0) {
var aMod4 = a and 3
while (aMod4 == 0) { // remove factors of four
a = a shr 2
aMod4 = a and 3
}
if (aMod4 == 2) { // if even
a = a shr 1 // remove factor 2 and possibly change sign
if ((n and 7).let { it == 3 || it == 5 })
result = -result
aMod4 = a and 3
}
if (aMod4 == 3 && n and 3 == 3)
result = -result
a = (n % a).also { n = a }
}
return if (n == 1) result else 0
}

Perl[edit]

Translation of: Raku
use strict;
use warnings;
 
sub J {
my($k,$n) = @_;
 
$k %= $n;
my $jacobi = 1;
while ($k) {
while (0 == $k % 2) {
$k = int $k / 2;
$jacobi *= -1 if $n%8 == 3 or $n%8 == 5;
}
($k, $n) = ($n, $k);
$jacobi *= -1 if $n%4 == 3 and $k%4 == 3;
$k %= $n;
}
$n == 1 ? $jacobi : 0
}
 
my $maxa = 1 + (my $maxn = 29);
 
print 'n\k';
printf '%4d', $_ for 1..$maxa;
print "\n";
print ' ' . '-' x (4 * $maxa) . "\n";
 
for my $n (1..$maxn) {
next if 0 == $n % 2;
printf '%3d', $n;
printf '%4d', J($_, $n) for 1..$maxa;
print "\n"
}
Output:
n\k   1   2   3   4   5   6   7   8   9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30
   ------------------------------------------------------------------------------------------------------------------------
  1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1
  3   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0
  5   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0
  7   1   1  -1   1  -1  -1   0   1   1  -1   1  -1  -1   0   1   1  -1   1  -1  -1   0   1   1  -1   1  -1  -1   0   1   1
  9   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0
 11   1  -1   1   1   1  -1  -1  -1   1  -1   0   1  -1   1   1   1  -1  -1  -1   1  -1   0   1  -1   1   1   1  -1  -1  -1
 13   1  -1   1   1  -1  -1  -1  -1   1   1  -1   1   0   1  -1   1   1  -1  -1  -1  -1   1   1  -1   1   0   1  -1   1   1
 15   1   1   0   1   0   0  -1   1   0   0  -1   0  -1  -1   0   1   1   0   1   0   0  -1   1   0   0  -1   0  -1  -1   0
 17   1   1  -1   1  -1  -1  -1   1   1  -1  -1  -1   1  -1   1   1   0   1   1  -1   1  -1  -1  -1   1   1  -1  -1  -1   1
 19   1  -1  -1   1   1   1   1  -1   1  -1   1  -1  -1  -1  -1   1   1  -1   0   1  -1  -1   1   1   1   1  -1   1  -1   1
 21   1  -1   0   1   1   0   0  -1   0  -1  -1   0  -1   0   0   1   1   0  -1   1   0   1  -1   0   1   1   0   0  -1   0
 23   1   1   1   1  -1   1  -1   1   1  -1  -1   1   1  -1  -1   1  -1   1  -1  -1  -1  -1   0   1   1   1   1  -1   1  -1
 25   1   1   1   1   0   1   1   1   1   0   1   1   1   1   0   1   1   1   1   0   1   1   1   1   0   1   1   1   1   0
 27   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0
 29   1  -1  -1   1   1   1   1  -1   1  -1  -1  -1   1  -1  -1   1  -1  -1  -1   1  -1   1   1   1   1  -1  -1   1   0   1

Phix[edit]

function jacobi(integer a, n)
atom result = 1
a = remainder(a,n)
while a!=0 do
while remainder(a,2)==0 do
a /= 2
if find(remainder(n,8),{3,5}) then result *= -1 end if
end while
{a, n} = {n, a}
if remainder(a,4)==3 and remainder(n,4)==3 then result *= -1 end if
a = remainder(a,n)
end while
return iff(n==1 ? result : 0)
end function
 
printf(1,"n\\a 0 1 2 3 4 5 6 7 8 9 10 11\n")
printf(1," ________________________________________________\n")
for n=1 to 31 by 2 do
printf(1,"%3d", n)
for a=0 to 11 do
printf(1,"%4d",jacobi(a, n))
end for
printf(1,"\n")
end for
Output:
n\a   0   1   2   3   4   5   6   7   8   9  10  11
   ________________________________________________
  1   1   1   1   1   1   1   1   1   1   1   1   1
  3   0   1  -1   0   1  -1   0   1  -1   0   1  -1
  5   0   1  -1  -1   1   0   1  -1  -1   1   0   1
  7   0   1   1  -1   1  -1  -1   0   1   1  -1   1
  9   0   1   1   0   1   1   0   1   1   0   1   1
 11   0   1  -1   1   1   1  -1  -1  -1   1  -1   0
 13   0   1  -1   1   1  -1  -1  -1  -1   1   1  -1
 15   0   1   1   0   1   0   0  -1   1   0   0  -1
 17   0   1   1  -1   1  -1  -1  -1   1   1  -1  -1
 19   0   1  -1  -1   1   1   1   1  -1   1  -1   1
 21   0   1  -1   0   1   1   0   0  -1   0  -1  -1
 23   0   1   1   1   1  -1   1  -1   1   1  -1  -1
 25   0   1   1   1   1   0   1   1   1   1   0   1
 27   0   1  -1   0   1  -1   0   1  -1   0   1  -1
 29   0   1  -1  -1   1   1   1   1  -1   1  -1  -1
 31   0   1   1  -1   1   1  -1   1   1   1   1  -1

Python[edit]

def jacobi(a, n):
if n <= 0:
raise ValueError("'n' must be a positive integer.")
if n % 2 == 0:
raise ValueError("'n' must be odd.")
a %= n
result = 1
while a != 0:
while a % 2 == 0:
a /= 2
n_mod_8 = n % 8
if n_mod_8 in (3, 5):
result = -result
a, n = n, a
if a % 4 == 3 and n % 4 == 3:
result = -result
a %= n
if n == 1:
return result
else:
return 0

Raku[edit]

(formerly Perl 6)

Works with: Rakudo version 2019.11
# Jacobi function
sub infix:<J> (Int $k is copy, Int $n is copy where * % 2) {
$k %= $n;
my $jacobi = 1;
while $k {
while $k %% 2 {
$k div= 2;
$jacobi *= -1 if $n % 8 == 3 | 5;
}
($k, $n) = $n, $k;
$jacobi *= -1 if 3 == $n%4 & $k%4;
$k %= $n;
}
$n == 1 ?? $jacobi !! 0
}
 
# Testing
 
my $maxa = 30;
my $maxn = 29;
 
say 'n\k ', (1..$maxa).fmt: '%3d';
say ' ', '-' x 4 * $maxa;
for 1,*+2$maxn -> $n {
print $n.fmt: '%3d';
for 1..$maxa -> $k {
print ($k J $n).fmt: '%4d';
}
print "\n";
}
Output:
n\k   1   2   3   4   5   6   7   8   9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30
   ------------------------------------------------------------------------------------------------------------------------
  1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1
  3   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0
  5   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0
  7   1   1  -1   1  -1  -1   0   1   1  -1   1  -1  -1   0   1   1  -1   1  -1  -1   0   1   1  -1   1  -1  -1   0   1   1
  9   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0
 11   1  -1   1   1   1  -1  -1  -1   1  -1   0   1  -1   1   1   1  -1  -1  -1   1  -1   0   1  -1   1   1   1  -1  -1  -1
 13   1  -1   1   1  -1  -1  -1  -1   1   1  -1   1   0   1  -1   1   1  -1  -1  -1  -1   1   1  -1   1   0   1  -1   1   1
 15   1   1   0   1   0   0  -1   1   0   0  -1   0  -1  -1   0   1   1   0   1   0   0  -1   1   0   0  -1   0  -1  -1   0
 17   1   1  -1   1  -1  -1  -1   1   1  -1  -1  -1   1  -1   1   1   0   1   1  -1   1  -1  -1  -1   1   1  -1  -1  -1   1
 19   1  -1  -1   1   1   1   1  -1   1  -1   1  -1  -1  -1  -1   1   1  -1   0   1  -1  -1   1   1   1   1  -1   1  -1   1
 21   1  -1   0   1   1   0   0  -1   0  -1  -1   0  -1   0   0   1   1   0  -1   1   0   1  -1   0   1   1   0   0  -1   0
 23   1   1   1   1  -1   1  -1   1   1  -1  -1   1   1  -1  -1   1  -1   1  -1  -1  -1  -1   0   1   1   1   1  -1   1  -1
 25   1   1   1   1   0   1   1   1   1   0   1   1   1   1   0   1   1   1   1   0   1   1   1   1   0   1   1   1   1   0
 27   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0
 29   1  -1  -1   1   1   1   1  -1   1  -1  -1  -1   1  -1  -1   1  -1  -1  -1   1  -1   1   1   1   1  -1  -1   1   0   1

REXX[edit]

Translation of: Go


A little extra code was added to make a prettier grid.

/*REXX pgm computes/displays the Jacobi symbol, the # of rows & columns can be specified*/
parse arg rows cols . /*obtain optional arguments from the CL*/
if rows='' | rows=="," then rows= 17 /*Not specified? Then use the default.*/
if cols='' | cols=="," then cols= 16 /* " " " " " " */
call hdrs /*display the (two) headers to the term*/
do r=1 by 2 to rows; _= right(r, 3) /*build odd (numbered) rows of a table.*/
do c=0 to cols /* [↓] build a column for a table row.*/
_= _ ! right(jacobi(c, r), 2);  != '│' /*reset grid end char.*/
end /*c*/
say _ '║';  != '║' /*display a table row; reset grid glyph*/
end /*r*/
say translate(@.2, '╩╧╝', "╬╤╗") /*display the bottom of the grid border*/
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
hdrs: @.1= 'n/a ║'; do c=0 to cols; @.1= @.1 || right(c, 3)" "; end
L= length(@.1); @.1= left(@.1, L - 1)  ; say @.1
@.2= '════╬'; do c=0 to cols; @.2= @.2 || "════╤"  ; end
L= length(@.2); @.2= left(@.2, L - 1)"╗" ; say @.2
 != '║'  ; return /*define an external grid border glyph.*/
/*──────────────────────────────────────────────────────────────────────────────────────*/
jacobi: procedure; parse arg a,n; er= '***error***'; $ = 1 /*define result.*/
if n//2==0 then do; say er n " must be a positive odd integer."; exit 13
end
a= a // n /*obtain A modulus N */
do while a\==0 /*perform while A isn't zero. */
do while a//2==0; a= a % 2 /*divide A (as a integer) by 2 */
if n//8==3 | n//8==5 then $= -$ /*use N mod 8 */
end /*while a//2==0*/
parse value a n with n a /*swap values of variables: A N */
if a//4==3 & n//4==3 then $= -$ /* A mod 4, N mod 4. Both ≡ 3 ?*/
a= a // n /*obtain A modulus N */
end /*while a\==0*/
if n==1 then return $
return 0
output   when using the default inputs:
n/a ║  0    1    2    3    4    5    6    7    8    9   10   11   12   13   14   15   16
════╬════╤════╤════╤════╤════╤════╤════╤════╤════╤════╤════╤════╤════╤════╤════╤════╤════╗
  1 ║  1 │  1 │  1 │  1 │  1 │  1 │  1 │  1 │  1 │  1 │  1 │  1 │  1 │  1 │  1 │  1 │  1 ║
  3 ║  0 │  1 │ -1 │  0 │  1 │ -1 │  0 │  1 │ -1 │  0 │  1 │ -1 │  0 │  1 │ -1 │  0 │  1 ║
  5 ║  0 │  1 │ -1 │ -1 │  1 │  0 │  1 │ -1 │ -1 │  1 │  0 │  1 │ -1 │ -1 │  1 │  0 │  1 ║
  7 ║  0 │  1 │  1 │ -1 │  1 │ -1 │ -1 │  0 │  1 │  1 │ -1 │  1 │ -1 │ -1 │  0 │  1 │  1 ║
  9 ║  0 │  1 │  1 │  0 │  1 │  1 │  0 │  1 │  1 │  0 │  1 │  1 │  0 │  1 │  1 │  0 │  1 ║
 11 ║  0 │  1 │ -1 │  1 │  1 │  1 │ -1 │ -1 │ -1 │  1 │ -1 │  0 │  1 │ -1 │  1 │  1 │  1 ║
 13 ║  0 │  1 │ -1 │  1 │  1 │ -1 │ -1 │ -1 │ -1 │  1 │  1 │ -1 │  1 │  0 │  1 │ -1 │  1 ║
 15 ║  0 │  1 │  1 │  0 │  1 │  0 │  0 │ -1 │  1 │  0 │  0 │ -1 │  0 │ -1 │ -1 │  0 │  1 ║
 17 ║  0 │  1 │  1 │ -1 │  1 │ -1 │ -1 │ -1 │  1 │  1 │ -1 │ -1 │ -1 │  1 │ -1 │  1 │  1 ║
════╩════╧════╧════╧════╧════╧════╧════╧════╧════╧════╧════╧════╧════╧════╧════╧════╧════╝

Ruby[edit]

Translation of: Crystal
def jacobi(a, n)
raise ArgumentError.new "n must b positive and odd" if n < 1 || n.even?
res = 1
until (a %= n) == 0
while a.even?
a >>= 1
res = -res if [3, 5].include? n % 8
end
a, n = n, a
res = -res if [a % 4, n % 4] == [3, 3]
end
n == 1 ? res : 0
end
 
puts "Jacobian symbols for jacobi(a, n)"
puts "n\\a 0 1 2 3 4 5 6 7 8 9 10"
puts "------------------------------------"
1.step(to: 17, by: 2) do |n|
printf("%2d ", n)
(0..10).each { |a| printf(" % 2d", jacobi(a, n)) }
puts
end
Output:
Jacobian symbols for jacobi(a, n)
n\a  0  1  2  3  4  5  6  7  8  9 10
------------------------------------
 1   1  1  1  1  1  1  1  1  1  1  1
 3   0  1 -1  0  1 -1  0  1 -1  0  1
 5   0  1 -1 -1  1  0  1 -1 -1  1  0
 7   0  1  1 -1  1 -1 -1  0  1  1 -1
 9   0  1  1  0  1  1  0  1  1  0  1
11   0  1 -1  1  1  1 -1 -1 -1  1 -1
13   0  1 -1  1  1 -1 -1 -1 -1  1  1
15   0  1  1  0  1  0  0 -1  1  0  0
17   0  1  1 -1  1 -1 -1 -1  1  1 -1

Rust[edit]

Translation of: C++
fn jacobi(mut n: i32, mut k: i32) -> i32 {
assert!(k > 0 && k % 2 == 1);
n %= k;
let mut t = 1;
while n != 0 {
while n % 2 == 0 {
n /= 2;
let r = k % 8;
if r == 3 || r == 5 {
t = -t;
}
}
std::mem::swap(&mut n, &mut k);
if n % 4 == 3 && k % 4 == 3 {
t = -t;
}
n %= k;
}
if k == 1 {
t
} else {
0
}
}
 
fn print_table(kmax: i32, nmax: i32) {
print!("n\\k|");
for k in 0..=kmax {
print!(" {:2}", k);
}
print!("\n----");
for _ in 0..=kmax {
print!("---");
}
println!();
for n in (1..=nmax).step_by(2) {
print!("{:2} |", n);
for k in 0..=kmax {
print!(" {:2}", jacobi(k, n));
}
println!();
}
}
 
fn main() {
print_table(20, 21);
}
Output:
n\k|  0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20
-------------------------------------------------------------------
 1 |  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1
 3 |  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1  0  1 -1
 5 |  0  1 -1 -1  1  0  1 -1 -1  1  0  1 -1 -1  1  0  1 -1 -1  1  0
 7 |  0  1  1 -1  1 -1 -1  0  1  1 -1  1 -1 -1  0  1  1 -1  1 -1 -1
 9 |  0  1  1  0  1  1  0  1  1  0  1  1  0  1  1  0  1  1  0  1  1
11 |  0  1 -1  1  1  1 -1 -1 -1  1 -1  0  1 -1  1  1  1 -1 -1 -1  1
13 |  0  1 -1  1  1 -1 -1 -1 -1  1  1 -1  1  0  1 -1  1  1 -1 -1 -1
15 |  0  1  1  0  1  0  0 -1  1  0  0 -1  0 -1 -1  0  1  1  0  1  0
17 |  0  1  1 -1  1 -1 -1 -1  1  1 -1 -1 -1  1 -1  1  1  0  1  1 -1
19 |  0  1 -1 -1  1  1  1  1 -1  1 -1  1 -1 -1 -1 -1  1  1 -1  0  1
21 |  0  1 -1  0  1  1  0  0 -1  0 -1 -1  0 -1  0  0  1  1  0 -1  1

Scala[edit]

 
def jacobi(a_p: Int, n_p: Int): Int =
{
var a = a_p
var n = n_p
if (n <= 0) return -1
if (n % 2 == 0) return -1
 
a %= n
var result = 1
while (a != 0) {
while (a % 2 == 0) {
a /= 2
if (n % 8 == 3 || n % 8 == 5) result = -result
}
val t = a
a = n
n = t
if (a % 4 == 3 && n % 4 == 3) result = -result
a %= n
}
if (n != 1) result = 0
 
result
}
 
def main(args: Array[String]): Unit =
{
for {
a <- 0 until 11
n <- 1 until 31 by 2
} yield println("n = " + n + ", a = " + a + ": " + jacobi(a, n))
}
 
output:
n = 1, a = 0: 1

n = 3, a = 0: 0

n = 5, a = 0: 0

n = 7, a = 0: 0

n = 9, a = 0: 0

n = 1, a = 1: 1

n = 3, a = 1: 1

n = 5, a = 1: 1

n = 7, a = 1: 1

n = 9, a = 1: 1

n = 1, a = 2: 1

n = 3, a = 2: -1

n = 5, a = 2: -1

n = 7, a = 2: 1

n = 9, a = 2: 1

n = 1, a = 3: 1

n = 3, a = 3: 0

n = 5, a = 3: -1

n = 7, a = 3: -1

n = 9, a = 3: 0

n = 1, a = 4: 1

n = 3, a = 4: 1

n = 5, a = 4: 1

n = 7, a = 4: 1

n = 9, a = 4: 1

n = 1, a = 5: 1

n = 3, a = 5: -1

n = 5, a = 5: 0

n = 7, a = 5: -1

n = 9, a = 5: 1

n = 1, a = 6: 1

n = 3, a = 6: 0

n = 5, a = 6: 1

n = 7, a = 6: -1

n = 9, a = 6: 0

n = 1, a = 7: 1

n = 3, a = 7: 1

n = 5, a = 7: -1

n = 7, a = 7: 0

n = 9, a = 7: 1

n = 1, a = 8: 1

n = 3, a = 8: -1

n = 5, a = 8: -1

n = 7, a = 8: 1

n = 9, a = 8: 1

n = 1, a = 9: 1

n = 3, a = 9: 0

n = 5, a = 9: 1

n = 7, a = 9: 1

n = 9, a = 9: 0

n = 1, a = 10: 1

n = 3, a = 10: 1

n = 5, a = 10: 0

n = 7, a = 10: -1

n = 9, a = 10: 1

Scheme[edit]

(define jacobi (lambda (a n)
(let ((a-mod-n (modulo a n)))
(if (zero? a-mod-n)
(if (= n 1)
1
0)
(if (even? a-mod-n)
(case (modulo n 8)
((3 5) (- (jacobi (/ a-mod-n 2) n)))
((1 7) (jacobi (/ a-mod-n 2) n)))
(if (and (= (modulo a-mod-n 4) 3) (= (modulo n 4) 3))
(- (jacobi n a-mod-n))
(jacobi n a-mod-n)))))))

Sidef[edit]

Also built-in as kronecker(n,k).

func jacobi(n, k) {
 
assert(k > 0, "#{k} must be positive")
assert(k.is_odd, "#{k} must be odd")
 
var t = 1
while (n %= k) {
var v = n.valuation(2)
t *= (-1)**v if (k%8 ~~ [3,5])
n >>= v
(n,k) = (k,n)
t = -t if ([n%4, k%4] == [3,3])
}
 
k==1 ? t : 0
}
 
for n in (0..50), k in (0..50) {
assert_eq(jacobi(n, 2*k + 1), kronecker(n, 2*k + 1))
}

Swift[edit]

import Foundation
 
func jacobi(a: Int, n: Int) -> Int {
var a = a % n
var n = n
var res = 1
 
while a != 0 {
while a & 1 == 0 {
a >>= 1
 
if n % 8 == 3 || n % 8 == 5 {
res = -res
}
}
 
(a, n) = (n, a)
 
if a % 4 == 3 && n % 4 == 3 {
res = -res
}
 
a %= n
}
 
return n == 1 ? res : 0
}
 
print("n/a 0 1 2 3 4 5 6 7 8 9")
print("---------------------------------")
 
for n in stride(from: 1, through: 17, by: 2) {
print(String(format: "%2d", n), terminator: "")
 
for a in 0..<10 {
print(String(format: " % d", jacobi(a: a, n: n)), terminator: "")
}
 
print()
}
Output:
n/a  0  1  2  3  4  5  6  7  8  9
---------------------------------
 1  1  1  1  1  1  1  1  1  1  1
 3  0  1 -1  0  1 -1  0  1 -1  0
 5  0  1 -1 -1  1  0  1 -1 -1  1
 7  0  1  1 -1  1 -1 -1  0  1  1
 9  0  1  1  0  1  1  0  1  1  0
11  0  1 -1  1  1  1 -1 -1 -1  1
13  0  1 -1  1  1 -1 -1 -1 -1  1
15  0  1  1  0  1  0  0 -1  1  0
17  0  1  1 -1  1 -1 -1 -1  1  1

Wren[edit]

Translation of: Python
Library: Wren-fmt
import "/fmt" for Fmt
 
var jacobi = Fn.new { |a, n|
if (!n.isInteger || n <= 0 || n%2 == 0) {
Fiber.abort("The 'n' parameter must be an odd positive integer.")
}
a = a % n
var result = 1
while (a != 0) {
while (a%2 == 0) {
a = a / 2
var nm8 = n % 8
if ([3, 5].contains(nm8)) result = -result
}
var t = a
a = n
n = t
if (a%4 == 3 && n%4 == 3) result = -result
a = a % n
}
return (n == 1) ? result : 0
}
 
System.print("Table of jacobi(a, n):")
System.print("n/a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15")
System.print("---------------------------------------------------------------")
var n = 1
while (n < 31) {
System.write(Fmt.d(3, n))
for (a in 1..15) System.write(Fmt.d(4, jacobi.call(a, n)))
System.print()
n = n + 2
}
Output:
Table of jacobi(a, n):
n/a   1   2   3   4   5   6   7   8   9  10  11  12  13  14  15
---------------------------------------------------------------
  1   1   1   1   1   1   1   1   1   1   1   1   1   1   1   1
  3   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0
  5   1  -1  -1   1   0   1  -1  -1   1   0   1  -1  -1   1   0
  7   1   1  -1   1  -1  -1   0   1   1  -1   1  -1  -1   0   1
  9   1   1   0   1   1   0   1   1   0   1   1   0   1   1   0
 11   1  -1   1   1   1  -1  -1  -1   1  -1   0   1  -1   1   1
 13   1  -1   1   1  -1  -1  -1  -1   1   1  -1   1   0   1  -1
 15   1   1   0   1   0   0  -1   1   0   0  -1   0  -1  -1   0
 17   1   1  -1   1  -1  -1  -1   1   1  -1  -1  -1   1  -1   1
 19   1  -1  -1   1   1   1   1  -1   1  -1   1  -1  -1  -1  -1
 21   1  -1   0   1   1   0   0  -1   0  -1  -1   0  -1   0   0
 23   1   1   1   1  -1   1  -1   1   1  -1  -1   1   1  -1  -1
 25   1   1   1   1   0   1   1   1   1   0   1   1   1   1   0
 27   1  -1   0   1  -1   0   1  -1   0   1  -1   0   1  -1   0
 29   1  -1  -1   1   1   1   1  -1   1  -1  -1  -1   1  -1  -1

zkl[edit]

fcn jacobi(a,n){
if(n.isEven or n<1)
throw(Exception.ValueError("'n' must be a positive odd integer"));
a=a%n; result,t := 1,0;
while(a!=0){
while(a.isEven){
a/=2; n_mod_8:=n%8;
if(n_mod_8==3 or n_mod_8==5) result=-result;
}
t,a,n = a,n,t;
if(a%4==3 and n%4==3) result=-result;
a=a%n;
}
if(n==1) result else 0
}
println("Using hand-coded version:");
println("n/a 0 1 2 3 4 5 6 7 8 9");
println("---------------------------------");
foreach n in ([1..17,2]){
print("%2d ".fmt(n));
foreach a in (10){ print(" % d".fmt(jacobi(a,n))) }
println();
}
Library: GMP
GNU Multiple Precision Arithmetic Library
var [const] BI=Import.lib("zklBigNum");  // libGMP
println("\nUsing BigInt library function:");
println("n/a 0 1 2 3 4 5 6 7 8 9");
println("---------------------------------");
foreach n in ([1..17,2]){
print("%2d ".fmt(n));
foreach a in (10){ print(" % d".fmt(BI(a).jacobi(n))) }
println();
}
Output:
Using hand-coded version:
n/a  0  1  2  3  4  5  6  7  8  9
---------------------------------
 1   1  1  1  1  1  1  1  1  1  1
 3   0  1 -1  0  1 -1  0  1 -1  0
 5   0  1 -1 -1  1  0  1 -1 -1  1
 7   0  1  1 -1  1 -1 -1  0  1  1
 9   0  1  1  0  1  1  0  1  1  0
11   0  1 -1  1  1  1 -1 -1 -1  1
13   0  1 -1  1  1 -1 -1 -1 -1  1
15   0  1  1  0  1  0  0 -1  1  0
17   0  1  1 -1  1 -1 -1 -1  1  1

Using BigInt library function:
n/a  0  1  2  3  4  5  6  7  8  9
---------------------------------
 1   1  1  1  1  1  1  1  1  1  1
 3   0  1 -1  0  1 -1  0  1 -1  0
 5   0  1 -1 -1  1  0  1 -1 -1  1
 7   0  1  1 -1  1 -1 -1  0  1  1
 9   0  1  1  0  1  1  0  1  1  0
11   0  1 -1  1  1  1 -1 -1 -1  1
13   0  1 -1  1  1 -1 -1 -1 -1  1
15   0  1  1  0  1  0  0 -1  1  0
17   0  1  1 -1  1 -1 -1 -1  1  1