When is it rational to use several programming languages ​​at once?

Question

Programming languages

In fact, almost every language has libraries that cover any whim of the developers, but I still sometimes see that some projects are done in several languages ​​​​at once, and it looks like a good shot in the foot.
When are such risks justified? And how to determine whether it is necessary to connect another language to the architecture or to get by with what is in the current one?

Answer 1

Ultimately, it all depends on the competencies of the team. If you have old robbers on your team who have been writing C ++ since 1995, you won’t even force them to write mathematical code in Python with a stick, although there are some “easier types” there.
The justification for stack growth is the need to adapt to the narrow specialization of tasks (writing queries to the DBMS in CSS is somewhat strange, as well as writing a front in SQL).
In short, language is a tool. If a well-delimited piece can be singled out in a project, for which there is a good tool, it is logical to use it, even if you have to hire someone for it.
But the idea to write a piece in Rust in a C++ project is “badass fashionable” - this is more of a problem than an idea.

Answer 2

St. Petersburg State University - ITMO, heard a lot about them and only positive.