[R] Handling very large integers with factorial and combinat (nCm)

[Marco Chiarandini]

Dear list,

perhpas this question is more suitable for R-dev but since I am not
really a developer I post it here first.

Apparently the following lines do not create any problem in R:

library(combinat)
r <- 20; b <- 2;
sum( sapply(0:r,function(x) nCm(r,x)^(2*b)) ) > 2^64

while in C I obtain an overflow of data even using unsigned long long
and with long double I incurr in precision problems.

Where can I find information about how R (or the combinat package)
handles very large integer numbers?


Thank you for consideration,


Marco