Editing Compiler-compiler (section)

===TREE-META===
{{main|TREE-META}}

TREE-META introduced tree building operators ''':'''<''node_name''> and '''['''<''number''>''']''' moving the output production transforms to unparsed rules. The tree building operators were used in the grammar rules directly transforming the input into an [[abstract syntax tree]]. Unparse rules are also test functions that matched tree patterns. Unparse rules are called from a grammar rule when an abstract syntax tree is to be transformed into output code. The building of an abstract syntax tree and unparse rules allowed local optimizations to be performed by analyzing the parse tree.

Moving of output productions to the unparse rules made a clear separation of grammar analysis and code production. This made the programming easier to read and understand.