error analysis of PI



the calculation of PI has
length      # of wrong digits

100              0
1000            1
10000          2
100000        3
1000000      4

so if you calculate PI to fpprec + log base 10  of fpprec
and then return fpprec digits then they all will be correct
I know it might be trivial but on known numbers like pi and e etc. it 
would be nice to be right. :-)

Doug Stewart