Circular primes: Difference between revisions
Added XPL0 example.
m (→{{header|Free Pascal}}: runtime 44% of before.Change counter so no no smaller digit than the first is used.Tested numbers mod 3/7 to speed up.) |
(Added XPL0 example.) |
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Line 2,823:
R(35317) : false
R(49081) : true
</pre>
=={{header|XPL0}}==
<lang XPL0>func IsPrime(N); \Return 'true' if N > 2 is a prime number
int N, I;
[if (N&1) = 0 \even number\ then return false;
for I:= 3 to sqrt(N) do
[if rem(N/I) = 0 then return false;
I:= I+1;
];
return true;
];
func CircPrime(N0); \Return 'true' if N0 is a circular prime
int N0, N, Digits, Rotation, I, R;
[N:= N0;
Digits:= 0; \count number of digits in N
repeat Digits:= Digits+1;
N:= N/10;
until N = 0;
N:= N0;
for Rotation:= 0 to Digits-1 do
[if not IsPrime(N) then return false;
N:= N/10; \rotate least sig digit into high end
R:= rem(0);
for I:= 0 to Digits-2 do
R:= R*10;
N:= N+R;
if N0 > N then \reject N0 if it has a smaller prime rotation
return false;
];
return true;
];
int Counter, N;
[IntOut(0, 2); ChOut(0, ^ ); \show first circular prime
Counter:= 1;
N:= 3; \remaining primes are odd
loop [if CircPrime(N) then
[IntOut(0, N); ChOut(0, ^ );
Counter:= Counter+1;
if Counter >= 19 then quit;
];
N:= N+2;
];
]</lang>
{{out}}
<pre>
2 3 5 7 11 13 17 37 79 113 197 199 337 1193 3779 11939 19937 193939 199933
</pre>
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