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#REDIRECT [[Help:Syntax Highlighting]]
[[Category:Less Than 20 Examples]]{{task}}[[Category:Prime Numbers]]
The following are examples of typical code formated with GeSHi.

==Supported source tags==
GeSHi currently supports the following tags: [[actionscript-french]], [[actionscript]], [[ada]], [[apache]], [[applescript]], [[asm]], [[asp]], [[bash]], [[blitzbasic]], [[caddcl]], [[cadlisp]], [[c_mac]], [[c]], [[C++|cpp]], [[csharp]], [[css]], [[delphi]], [[diff]], [[dos]], [[d]], [[eiffel]], [[freebasic]], [[gml]], [[html4strict]], [[ini]], [[inno]], [[java]], [[javascript]], [[lisp]], [[lua]], [[matlab]], [[mpasm]], [[mysql]], [[nsis]], [[objc]], [[ocaml-brief]], [[ocaml]], [[oobas]], [[oracle8]], [[pascal]], [[perl]], [[php-brief]], [[php]], [[python]], [[qbasic]], [[ruby]], [[scheme]], [[sdlbasic]], [[smarty]], [[sql]], [[vbnet]], [[vb]], [[vhdl]], [[visualfoxpro]] & [[xml]].

Use trial division. Even numbers may be eliminated right away. A loop from 3 to √(n) will suffice, but other loops are allowed.

=={{header|Ada}}==
<Ada>
function Is_Prime(Item : Positive) return Boolean is
Result : Boolean := True;
Test : Natural;
begin
if Item /= 2 and Item mod 2 = 0 then
Result := False;
else
Test := 3;
while Test < Integer(Sqrt(Float(Item))) loop
if Item mod Test = 0 then
Result := False;
exit;
end if;
Test := Test + 2;
end loop;
end if;
return Result;
end Is_Prime;
</Ada>

=={{header|ALGOL 68}}==
<ALGOL_68>
main:(
PROC is prime = ( INT n )BOOL:
(
IF n = 2 THEN
TRUE
ELIF n <= 1 OR n MOD 2 = 0 THEN
FALSE
ELSE
BOOL prime := TRUE;
FOR i FROM 3 BY 2 TO ENTIER sqrt(n) WHILE prime := n MOD i /= 0 DO
SKIP
OD;
prime
FI
);
INT upb=100;
printf(($" The primes up to "g(-3)" are:"l$,upb));
FOR i TO upb DO
IF is prime(i) THEN
printf(($g(-4)$,i))
FI
OD;
printf($l$)
)
Output:
</ALGOL_68>
The primes up to 100 are:
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97
=={{header|BASIC}}==
{{works with|QuickBasic|4.5}}

Going with the classic 1 for "true" and 0 for "false":
<qbasic>
FUNCTION prime% (n!)
IF n = 2 THEN prime = 1
IF n <= 1 OR n MOD 2 = 0 THEN prime = 0
FOR a = 3 TO INT(SQR(n)) STEP 2
IF n MOD a = 0 THEN prime = 0
NEXT a
prime = 1
END FUNCTION
</qbasic>

=={{header|C}}==
<C>
<source lang=C>
#include <math.h>
#define FALSE 0
#define TRUE 1
int isPrime( unsigned int n )
{
unsigned int i;
if ( n == 2 )
return TRUE;
if ( n <= 1 || ( n & 1 ) == 0 )
return FALSE;
for ( i = 3 ; i <= sqrt( n ) ; i += 2 )
if ( n % i == 0 )
return FALSE;
return TRUE;
}
</C>
=={{header|Common Lisp}}==
<Common Lisp>
(defun primep (a)
(cond ((= a 2) T)
((or (<= a 1) (= (mod a 2) 0)) nil)
((loop for i from 3 to (sqrt a) by 2 do
(if (= (mod a i) 0)
(return nil))) nil)
(T T)))
</Common Lisp>
=={{header|D}}==
<D>
import std.math: sqrt;
bool isPrime(int n) {
if (n == 2)
return true;
if (n <= 1 || (n & 1) == 0)
return false;
for(int i = 3; i <= sqrt(cast(float)n); i += 2)
if (n % i == 0)
return false;
return true;
}
</D>
=={{header|Forth}}==
<Forth>
: prime? ( n -- ? )
dup 2 < if drop false
else dup 2 = if drop true
else dup 1 and 0= if drop false
else 3
begin 2dup dup * >=
while 2dup mod 0=
if 2drop false exit
then 2 +
repeat 2drop true
then then then ;
</Forth>
=={{header|Haskell}}==

Without square roots:
<Haskell>
divides k n = n `mod` k == 0
isPrime :: Integer -> Bool
isPrime n | n < 2 = False
isPrime n = not $ any (`divides` n) $ takeWhile (\k -> k*k <= n) [2..]
</Haskell>
=={{header|J}}==

Actually <tt>1&p:</tt> would do, but the task calls for trial division, so:
<J>
isprime=: 3 : 'if. 3>:y do. 1<y else. 0 *./@:< y|~2+i.<.%:y end.'
</J>
=={{header|Java}}==
<Java>
public static boolean prime(double a){
if(a == 2){
return true;
}else if(a <= 1 || a % 2 == 0){
return false;
}
for(long n= 3; n <= (long)Math.sqrt(a); n+= 2){
if(a % n == 0){ return false; }
}
return true;
}
</Java>
=={{header|LSE64}}==
<LSE64>
over : 2 pick
2dup : over over
even? : 1 & 0 =
# trial n d yields "n d 0/1 false" or "n d+2 true"
trial : 2 + true
trial : 2dup % 0 = then 0 false
trial : 2dup dup * < then 1 false
trial-loop : trial &repeat
# prime? n yields flag
prime? : 3 trial-loop >flag drop drop
prime? : dup even? then drop false
prime? : dup 2 = then drop true
prime? : dup 2 < then drop false
</LSE64>
=={{header|MAXScript}}==
<MAXScript>
fn isPrime n =
(
if n == 2 then
(
return true
)
else if (n <= 1) OR (mod n 2 == 0) then
(
return false
)
for i in 3 to (sqrt n) by 2 do
(
if mod n i == 0 then return false
)
true
)
</MAXScript>
=={{header|Perl}}==
<Perl>
sub prime {
$a = shift;
if ($a == 2) {
return 1;
}
if ($a <= 1 || $a % 2 == 0) {
return 0;
}
$d = 3;
while ($d <= sqrt($a)) {
if ($a % $d == 0) {
return 0;
}
$d += 2;
}
return 1;
}
</Perl>
=={{header|Python}}==
The simplest primality test, using trial division:

{{works with|Python|2.5}}
<Python>
def prime(a):
return not (a < 2 or any(a % x == 0 for x in range(2, int(a**0.5) + 1)))
</Python>

Another test. Exclude even numbers first:

<Python>
def prime2(a):
if a == 2: return True
if a < 2 or a % 2 == 0: return False
return not any(a % x == 0 for x in range(3, int(a**0.5) + 1, 2))
</Python>

Yet another test. Exclude multiples of 2 and 3, see http://www.devx.com/vb2themax/Tip/19051:

{{works with|Python|2.4}}
<Python>
def prime3(a):
if a < 2: return False
if a == 2 or a == 3: return True # manually test 2 and 3
if a % 2 == 0 or a % 3 == 0: return False # exclude multiples of 2 and 3

maxDivisor = a**0.5
d, i = 5, 2
while d <= maxDivisor:
if a % d == 0: return False
d += i
i = 6 - i # this modifies 2 into 4 and viceversa

return True
</Python>

=={{header|Ruby}}==
<Ruby>
def prime(a)
if a==2
return true
end
if a<=1 || a%2==0
return false
end
d=3
while d <= Math.sqrt(a) do
if a%d==0
return false
end
d+=2
end
return true
end
</Ruby>
=={{header|TI-83 BASIC}}==
Calculator symbol translations:

"STO" arrow: →

Square root sign: √
<TI-83 BASIC>
Prompt A
If A=2:Then
Disp "PRIME"
Stop
End
If (fPart(A/2)=0 and A>0) or A<2:Then
Disp "NOT PRIME"
Stop
End
1→P
For(B,3,√(A))
If FPart(A/B)=0:Then
0→P
√(A)→B
End
B+1→B
End
If P=1:Then
Disp "PRIME"
Else
Disp "NOT PRIME"
End
</TI-83 BASIC>

Latest revision as of 21:42, 7 December 2009

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