(define-library (srfi 16)
  (export case-lambda)
  (import (chibi))
  (begin
   (define-syntax %case
     (syntax-rules ()
       ((%case args len n p ((params ...) . body) . rest)
        (if (= len (length '(params ...)))
            (apply (lambda (params ...) . body) args)
            (%case args len 0 () . rest)))
       ((%case args len n (p ...) ((x . y) . body) . rest)
        (%case args len (+ n 1) (p ... x) (y . body) . rest))
       ((%case args len n (p ...) (y . body) . rest)
        (if (>= len n)
            (apply (lambda (p ... . y) . body) args)
            (%case args len 0 () . rest)))
       ((%case args len n p)
        (error "case-lambda: no cases matched"))))
   (define-syntax case-lambda
     (syntax-rules ()
       ((case-lambda . clauses)
        (lambda args (let ((len (length* args))) (%case args len 0 () . clauses))))))))