# SRFI 147: Custom macro transformers

by Marc Nieper-Wißkirchen

status: final (2017/3/7)

## Abstract

Each syntax definition assigns a macro transformer to a keyword. The macro transformer is specified by a transformer spec, which is either an instance of syntax-rules, an existing syntactic keyword (including macro keywords and the syntactic keywords that introduce the core forms, like lambda, if, or define), or a use of a macro that eventually expands into an instance of syntax-rules. In the latter case, the keyword of macro use is called a custom macro transformer.