我需要读取一个Racket源文件并通过宏扩展来运行它 . 我有一个简单的测试文件,Racket自己乐意接受:
C:\ayane>type factorial.rkt
#lang racket
(provide factorial)
(define (factorial n)
(if (<= n 1)
1
(* n (factorial (sub1 n)))))
现在我尝试使用REPL:
C:\ayane>racket
Welcome to Racket v6.5.
> (read-accept-reader #t)
> (expand (with-input-from-file "factorial.rkt" (lambda () (read-syntax "factorial.rkt"))))
#<syntax::1 (module factorial racket (#%m...>
到现在为止还挺好 . 现在,测试程序也是如此:
C:\ayane>type test.rkt
#lang racket
(read-accept-reader #t)
(expand (with-input-from-file "factorial.rkt"
(lambda ()
(read-syntax "factorial.rkt"))))
C:\ayane>racket test.rkt
factorial.rkt::1: module: unbound identifier;
also, no #%app syntax transformer is bound
at: module
in: (module factorial racket (#%module-begin (provide factorial) (define (factorial n) (if (<= n 1) 1 (* n (factorial (sub1 n)))))))
context...:
C:\ayane\test.rkt: [running body]
所以看起来相同的代码交互式工作但不在程序中 . 我错过了什么?
2 回答
您需要指定
expand
应使用哪个命名空间来查找顶级变量(即未绑定在程序中的变量) .例如:
有关更多信息,请参阅下面文件中的注释,我将尝试解释命名空间和expand之间的关系:
https://github.com/soegaard/meta/blob/master/runtime/racket-eval.rkt#L122
@soegaard的答案解决了当前的问题,但是如果你想要一个全面的程序重新实现原语的扩展,你可以看看
https://github.com/samth/pycket/blob/master/pycket/pycket-lang/expand.rkt