Template:Prelude/is prime.a68

COMMENT
  This routine is used in more than one place, and is essentially a
  template that can by used for many different types, eg INT, LONG INT...
USAGE
  MODE ISPRIMEINT = INT, LONG INT, etc
  PR READ "prelude/is_prime.a68" PR
END COMMENT

PROC is prime = ( ISPRIMEINT p )BOOL:
  IF p <= 1 OR ( NOT ODD p AND p/= 2) THEN
    FALSE
  ELSE
    BOOL prime := TRUE;
    FOR i FROM 3 BY 2 TO ENTIER sqrt(p)
      WHILE prime := p MOD i /= 0 DO SKIP OD;
    prime
  FI

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This is a template. There are many others. See Category:RCTemplates for a complete list of templates.