Help:GeSHi

The following are examples of typical code formatted with GeSHi, the Generic Syntax Hilighter.

Supported source tags

This list is generated by the MediaWiki extension based on per-language syntax files available. Anything not in this list does not yet have syntax highlighting support on Rosetta Code. Feel free to provide a GeSHi script file. It will be reviewed and (probably) added. <lang list></lang>

Usage

All code should be formatted as follows:

<lang ada>
 Insert source code here.
</lang>

Replace "ada" with the language tag appropriate to the language of the code in question. It will be formatted using available syntax rules for the language.

The initial sample program

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

Ada

<lang 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;

</lang>

ALGOL 68 (unsupported)

<lang algol68>

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($l$)
)

</lang>

BASIC

Works with: QuickBasic version 4.5

Going with the classic 1 for "true" and 0 for "false": <lang 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

</lang>

C

<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;
}

</lang>

D

<lang 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;
}

</lang>

Forth (unsupported)

<lang 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 ;

</lang>

Groovy

Without even number avoidance: <lang groovy>def prime = { a ->

   a < 3 \
       ? a == 2 \
       : (2..([2,Math.sqrt(a)].max())).every { a % n != 0 }

}</lang>

Haskell

Without square roots: <lang 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..]

</lang>

J (unsupported)

Actually 1&p: would do, but the task calls for trial division, so: <lang j>

isprime=: 3 : 'if. 3>:y do. 1<y else. 0 *./@:< y|~2+i.<.%:y end.'

</lang>

Java

"<lang java>" example: <lang 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;
}

</lang> "<lang java5>" example: <lang java5>

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;
}

</lang>

Lisp

Note: Common Lisp words like "loop" are not highlighted. <lang 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)))</lang>

MAXScript (unsupported)

<lang 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
)

</lang>

Perl

<lang 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;
}

</lang>

Python

The simplest primality test, using trial division:

Works with: Python version 2.5

<lang python> def prime(a):

   return not (a < 2 or any(a % x === 0 for x in range(2, int(a**0.5) + 1)))

</lang>

Another test. Exclude even numbers first:

<lang 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))

</lang>

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

Works with: Python version 2.4

<lang 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

</lang>

Ruby

<lang 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

</lang>