This reminds me of the META [^1] II paper [^2]:

> META II is a domain-specific programming language for writing compilers. It was created in 1963–1964 by Dewey Val Schorre at University of California, Los Angeles (UCLA). META II uses what Schorre called syntax equations.

The interesting part of META II is that it can be defined in itself on one page (refer page 8 of the paper).

[^1] Wikipedia https://en.wikipedia.org/wiki/META_II

[^2] Paper: https://dl.acm.org/doi/epdf/10.1145/800257.808896