destructuring-bind.scm

(import
 (scheme base)
 (scheme write)
 (scheme cxr)
 (picrin macro))

(define-syntax destructuring-bind
  (ir-macro-transformer
   (lambda (form inject compare)
     (let ((pattern (cadr form))
	   (value   (caddr form))
	   (body    (cdddr form)))
       (cond ((null? pattern)
	      `(begin ,@body))
	     ((symbol? pattern)
	      `(let ((,pattern ,value)) (begin ,@body)))
	     ((pair? pattern)
	      `(let ((evaluated ,value))
		 (destructuring-bind ,(car pattern) (car evaluated)
		   (destructuring-bind ,(cdr pattern) (cdr evaluated)
		     ,@body)))))))))

(destructuring-bind (a b . c) '((1 2) 3 4 5) (list a b c)) ; ok
(destructuring-bind ((a b) . c) '((1 2) 3 4 5) (list a b c)) ; fail