[Wikidata] Big numbers

Is there any documentation of the number format used by the quantity type? Bumped into this and had to implement the BCmath extension to handle the number. The reason why I did it (except it was fun) is to handle some weird unit conversions. By inspection I found there were numbers at Wikidata that clearly could not be implemented as doubles, and testing a little I found that this had to be implemented as some kind of big numbers. Lua does not have big numbers, and using the numbers from quantity as a plain number type is a coming disaster. So, is there any documentation for the quantity format anywhere? I have not found anything. I posted a task about it, and please add info there if you know where some info can be found. I suspect the format just happen to be the same as BC, and nobody really checked if the format was compatible, or…? The BCmath extension can be found at - https://www.mediawiki.org/wiki/Extension:BCmath - https://github.com/jeblad/BCmath There is a Vagrant role if anyone likes to test it out.