Hiya, a bit of OT (again, last one promise!): I saw your comment about type systems in data science the other day (https://news.ycombinator.com/item?id=25923839). From what I understood, it seems you want a contract system, wouldn't you think? The reason I'm asking is that I'm fishing for opinions on building data science infra in Racket (and saw your deleted comment in https://news.ycombinator.com/item?id=26008869 so thought you'd perhaps be interested), and Racket (and R) dataframes happen to support contracts on their columns.