UIntlib 1.6 fixes a major bug in 1.5 where loading or linking more than one of the unsigned integer libraries at the same time could cause serious problems. Also I added a preprocessor for source files so that you can type, for instance, "0x300UL" instead of "(UInt64.of_string "0x300UL")". uintpre is just a text processor and so it won't work with the toplevel.