The current layout preprocessor renders tokens as String to check whether they match layout keywords or { } ;. However, each keyword/symbol token comes with an ID that could be checked faster.

Steps to rewrite layout processor (generator) to use IDs instead of String:

• LBNF: check whether { } ; occur in grammar when layout is used.
• Give each symbol a name, like ( is LPAREN.
• Define token constants in generated lexer for all the keywords and symbols.
• Reference these constants in the layouter, rather than strings.