Integer computation extended beyond 32-bit

compute integer arithmatic beyond 32-bit, Matlab's limit

% extending integer precision beyond 32-bit. Maximum integer value in
% Matlab is 'intmax = 2147483647'. This is a 'int' type in C. So if using
% 'intmax', double() must be used to convert it to double type in order to
% perform further computation. Others are by default double so no need of
% conversion.
% Reference: C Interfaces and Implmentations, David Hanson.