There are questions appearing on SO relating to relational algebra, of the general form 'Is my relational algebra correct?'. For questions like this relating to what one might term 'real' programming languages, I'll point out any glaring errors (if any) or nudge them in the direction of codereview
Relational algebra, while superficially similar to SQL, is not a 'real' programming language like PHP or c++ (or even SQL). The concept is more akin to mathematics, so is a question such as 'Is this relational algebra correct?' on-topic for SO?
If it isn't, what is an appropriate treatment? Should it be closed as off-topic with a nudge to codereview or some other site, or closed on some other basis, or simply ignored?