Gambas ONE

Pi can be calculated using the following formulas.

        Print Atn(1) * 4
        
        Print (4 * Atn(1 / 5) - Atn(1 / 239)) * 4

Of course, you don't need to do that because Gambas has:

        Print Pi(1)   ' = Pi * 1

But, if you want super precision, there is a Taylor series for the inverse tangent, and you can use arrays for digits...