diff --git a/README.md b/README.md index 82e8972..cc7a0c1 100644 --- a/README.md +++ b/README.md @@ -2,32 +2,3 @@ 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 ways to extend their syntax. For example, in the `match` form new patterns can be created for `match` using `define-match-expander`. This package provides a form for defining a macro with the ability to define expanders for that 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 package provides a form, `define-syntax-with-expanders`: - - (require generic-syntax-expanders) - - (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`.