I’m looking for an open-source algorithm that can generate sentences from a syntax structure.

In c++ preferably.
The structure would ideally be syntax fields such as noun, verb… Etc. And optional fields.

If there is a second version in Spanish would be great but I can do that research on my own.

I don’t want it to be Machine learning based as they hallucinate, and I have a limited GPU budget.

I’ve tried searching the algorithm using queries with -ai and in google scholar but I only found AI solutions and a 1965 paper that offered it in Russian due to data limitations at the time without giving it a name.

Thanks in advance!