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quasiquote is now safe for nesting

This commit is contained in:
Yuichi Nishiwaki 2014-02-12 22:31:17 +09:00
parent 234c573bb6
commit c69687d234
1 changed files with 47 additions and 16 deletions
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63
piclib/built-in.scm
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@ -120,24 +120,55 @@
(r 'it)
(cons (r 'or) (cdr exprs))))))))))
(define (quasiquote? form compare?)
(and (pair? form) (compare? (car form) 'quasiquote)))
(define (unquote? form compare?)
(and (pair? form) (compare? (car form) 'unquote)))
(define (unquote-splicing? form compare?)
(and (pair? form) (pair? (car form)) (compare? (car (car form)) 'unquote-splicing)))
(define-syntax quasiquote
(er-macro-transformer
(lambda (expr r compare?)
(let ((x (cadr expr)))
(ir-macro-transformer
(lambda (form inject compare)
(define (qq depth expr)
(cond
((symbol? x) (list (r 'quote) x))
((pair? x) (cond
((compare? (r 'unquote) (car x))
(cadr x))
((and (pair? (car x))
(compare? (r 'unquote-splicing) (caar x)))
(list (r 'append) (cadar x)
(list (r 'quasiquote) (cdr x))))
(#t
(list (r 'cons)
(list (r 'quasiquote) (car x))
(list (r 'quasiquote) (cdr x))))))
(#t x))))))
;; unquote
((unquote? expr compare)
(if (= depth 1)
(car (cdr expr))
(list 'list
(list 'quote (inject 'unquote))
(qq (- depth 1) (car (cdr expr))))))
;; unquote-splicing
((unquote-splicing? expr compare)
(if (= depth 1)
(list 'append
(car (cdr (car expr)))
(qq depth (cdr expr)))
(list 'cons
(list 'list
(list 'quote (inject 'unquote-splicing))
(qq (- depth 1) (car (cdr (car expr)))))
(qq depth (cdr expr)))))
;; quasiquote
((quasiquote? expr compare)
(list 'list
(list 'quote (inject 'quasiquote))
(qq (+ depth 1) (car (cdr expr)))))
;; list
((pair? expr)
(list 'cons
(qq depth (car expr))
(qq depth (cdr expr))))
;; simple datum
(else
(list 'quote expr))))
(let ((x (cadr form)))
(qq 1 x)))))
#;
(define-syntax let*