[Rd] simple add error (PR#13699)

[gostan at igmm.cnrs.fr]

Full_Name: Gostan Thierry
Version: 2.6.1 (2007-11-26)
OS: Windows XP
Submission from: (NULL) (193.49.190.42)


I cannot explain why R seems to have problems adding two big numbers.

sprintf("%f",10^4+10^19) gives "10000000000000010240.000000" 
                    instead of "10000000000000010000.000000"

problems seems to arrive when i'm trying to add a big and a small number...