**[**Back to MATH SWAG index**]** **[**Back to Main SWAG index**]** **[**Original**]**

```
```*(*I was looking for a faster sqr routine (still am), when I stumbled over
all of your prime
number programs. Although I don't know all about Turbo Pascal I do know
how to
make a faster Prime tester for Numbers < 31-bit, If you like it, copy it,
use routines
or whatever, but please think about leaving me credits
This program builds on the (theory) that a prime is always equal to
(X*6+1) or
(X*6-1) this I read of in a magazine. And it seems to work... I have with
this been
able to take lead (I think) with 50% faster routine than the others
by Tobias Olsson
*)
***Unit **Primtal;
**Interface
Function **Prime(Prim: LongInt): Boolean;
**implementation
Function **Prime(Prim: LongInt): Boolean;
**Var
**Z : Real;
Max : LongInt;
Divisor : LongInt;
**Begin
**Prime:= False;
**IF **(Prim **and **1) = 0 **then **Exit;
Z := Sqrt(Prim);
Max := Trunc(Z)+1;
Divisor := 3;
**While **Max > Divisor **do
Begin
IF **(Prim **mod **Divisor) = 0 **then **Exit;
Inc(Divisor,2);
**IF **(Prim **mod **Divisor) = 0 **then **Exit;
Inc(Divisor,4);
**End**;
Prime := True;
**End**;
**BEGIN
END**.

**[**Back to MATH SWAG index**]** **[**Back to Main SWAG index**]** **[**Original**]**