I was wondering if this is possible to implement or something you have thought a bit about?
For example, say I make a grid and want to constraints to it (e.g. each row must be greater or less than some value).

I have been trying this with expand.grid (because order does matter in my case) and data.table and finding it very time consuming and the required memory is quite large. I really liked the implementation in comboGeneral but it only applies to vectors.