Besides the documentation procedure, this module exports only one macro, local, which is inspired by the equally named operator in ML. It exports a list of definitions, depending on another hidden list of definitions. So it can be used to implement procedures depending on a common state, something what define-values can do as well. In this new version, the hidden definitions can be macros as well, but that enforces a small syntax change: you have to add the keywords define, define-syntax or what have you.
This documentation uses special ellipses meaning
- two dots: zero or one
- three dots: zero or many
- four dots: one or many occurences of the item to its left.
shows the definition of the local macro.
local[syntax] (local (def ...) (var val)|((var . args) . body) ....)
exports procedures var ... depending on hidden procedures or macros def ...
;; fake example (local ( (define-syntax xx (syntax-rules () ((_ x) (* x x)))) (define (yy y) 1 2 3 (+ y y)) (define zz 5) (define (uu u . us) #t) (define vv (lambda vs 10 20)) (define (ww . ws) #f) ) (aa (lambda (a) (+ zz (* 2 (xx a))))) ((bb b) 4 5 6 (* zz (* (xx b) (xx b)))) (cc (* 2 zz)) ((dd) (or (uu 10 20 30) (ww))) ((ee e) (vv #t #f))) ;; counter (local ( (state 0) ) ((counter-ref) state) ((counter-add!) (set! state (+ state 1))) ((counter-reset!) (set! state 0))) (counter-ref) ; -> 0 (counter-add!) (counter-add!) (counter-ref) ; -> 2 (counter-reset!) (counter-ref) ; -> 0
Dez 24, 2016
Copyright (c) 2016, Juergen Lorenz All rights reserved.
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- rewrite to accept macros
- initial import