Hello Andrew, Very clearly a bug. Comes from a bug in the log function (well, the more precise internal version that is used when computing powers) in the range [1.00099009, 1.0009901) it seems, and probably some other ranges. I'll investigate. Also, I'll likely answer at some point in the next couple of days to your juxtaposition email. Sorry for the delay. Regards, Bruno On 6/18/14, aparsloe <[log in to unmask]> wrote: > \fp_eval:n { exp(1) - (1+1/1009)^{1009} } -> 0.001346 > \fp_eval:n { exp(1) - (1+1/1010)^{1010} } -> 0.001613 > \fp_eval:n { exp(1) - (1+1/1011)^{1011} } -> 0.001343