[standevbob]

Stan requires models to be coded in the Stan language, which is a simple imperative language that's like MATLAB with explicit data types. This is the same as was done in Stan's predecessors, BUGS and JAGS.

A Stan program can be run in any of our interfaces in Python, Julia, R, MATLAB, Stata, etc. But you can't mix any of those languages into a Stan program.

The C++ toolchain is required because Stan transpiles its programs to C++, then compiles those against the Stan math librarym, which does autodiff. But you don't need to write any C++ to use Stan, just to develop extensions for it.