Parsing statements of the metalanguage resemble augmented Backus–Naur form with embedded tree-building directives.
Unparsing[1] rules include extensive tree-scanning and code-generation constructs.
TREE-META was instrumental in the development of NLS (oN-Line System) and was ported to many systems including the UNIVAC 1108, GE 645, SDS 940, ICL 1906A, PERQ, and UCSD p-System.
This program is not just a recognizer, but also outputs the assembly language for the input.
It demonstrates one of the key features of TREE-META, which is tree pattern matching.