Task

Write a boolean function that tells whether a given integer is prime.



Remember that   1   and all non-positive numbers are not prime.

Use trial division.

Even numbers greater than   2   may be eliminated right away.

A loop from   3   to   √ n    will suffice,   but other loops are allowed.



Related tasks

   count in factors
   prime decomposition
   AKS test for primes
   factors of an integer
   Sieve of Eratosthenes
   factors of a Mersenne number
   trial factoring of a Mersenne number
   partition an integer X into N primes
   sequence of primes by Trial Division


function IsPrime(aNumber: Integer): Boolean;
var
  I: Integer;
begin
  Result:= True;
  if(aNumber = 2) then Exit;
 
  Result:= not ((aNumber mod 2 = 0)  or
                (aNumber <= 1));
  if not Result then Exit;
 
  for I:=3 to Trunc(Sqrt(aNumber)) do
  if(aNumber mod I = 0) then
  begin
    Result:= False;
    Break;
  end;
end;