generic-syntax-expanders ======================== A Racket package for creating macros with built-in support for defining sub-macros within them, similar to match expanders Sometimes complex Racket macros need a way for their syntax to be extended. The Racket match form is an example, new patterns can be created for match using define-match-expander. This racket package provides a form for defining a macro with the ability to define expanders for the macro. Consider this contrived example: (define-syntax call-each (syntax-parser [(_ f (expr ...)) #'(begin (f expr) ...)])) (call-each displayln (1 2 3)) If a user of this macro wished for a way to specify a range of numbers as the arguments, the user must define their own version of call-each with support for ranges that expands to using the original call-each. However, this racket package provides a form, define-syntax-with-expanders: (require generic-syntax-expanders (for-syntax racket/list)) (define-syntax-with-expanders call-each (syntax-parser [(_ f (expr ...)) #'(begin (f expr) ... )])) (define-call-each-expander foo (syntax-parser [(_ low:number high:number) #`(#,@(range (syntax-e #'low) (syntax-e #'high)))])) (call-each displayln (foo 1 4)) The define-syntax-with-expanders form creates a define-call-each-expander form, which defines syntax transformers that are only used inside the body of a call-each form and expand before call-each does. You can install this package with `raco package install generic-syntax-expanders`.