11.sld

(define-library (srfi 11)
  (export let-values let*-values)
  (import (chibi))
  (begin
   (define-syntax let*-values
     (syntax-rules ()
       ((let*-values () . body)
        (let () . body))
       ((let*-values (((a) expr) . rest) . body)
        (let ((a expr)) (let*-values rest . body)))
       ((let*-values ((params expr) . rest) . body)
        (call-with-values (lambda () expr)
          (lambda params (let*-values rest . body))))))
   (define-syntax let-values
     (syntax-rules ()
       ((let-values () . body)
        (let () . body))
       ((let-values ("step") (binds ...) bind expr maps () () . body)
        (let*-values (binds ... (bind expr)) (let maps . body)))
       ((let-values ("step") (binds ...) bind old-expr maps () ((params expr) . rest) . body)
        (let-values ("step") (binds ... (bind old-expr)) () expr maps params rest . body))
       ((let-values ("step") binds (bind ...) expr (maps ...) (x . y) rest . body)
        (let-values ("step") binds (bind ... tmp) expr (maps ... (x tmp)) y rest . body))
       ((let-values ("step") binds (bind ...) expr (maps ...) x rest . body)
        (let-values ("step") binds (bind ... . tmp) expr (maps ... (x tmp)) () rest . body))
       ((let-values ((params expr) . rest) . body)
        (let-values ("step") () () expr () params rest . body))))))