There was a ticket elsewhere about supporting 64-bit unixtime by returning a list of the two halves of a 64-bit int, 32 bits wide. (32-bit ints run out for that purpose in about ten years.) There are probably other reasons you'd want to store a 64-bit int or float, like astronomical calculations. Is this going to be possible in Lua, or in LSL after the Lua cutover, without scripters writing a BCD layer or some other Rube Goldberg solution?
